ARDMS Obstetrics and Gynecology (OB/GYN) Specialty Examination — Questions and Answers

Question 1: What does M-mode ultrasound assess in the first trimester?

Fetal cardiac activity and heart rate (Correct answer)
Cervical length
Uterine artery flow
Yolk sac size

Correct answer: Fetal cardiac activity and heart rate

M-mode (motion mode) ultrasound is used to document and measure fetal cardiac activity and heart rate in the first trimester without using pulsed Doppler.

Question 2: What is the double decidual sac sign (DDSS)?

The appearance of a bicornuate uterus
Two concentric rings of decidua surrounding the gestational sac, confirming intrauterine location (Correct answer)
A sign of ectopic pregnancy
A twin pregnancy

Correct answer: Two concentric rings of decidua surrounding the gestational sac, confirming intrauterine location

The DDSS describes two concentric echogenic rings surrounding the gestational sac — the decidua capsularis and decidua parietalis — confirming intrauterine implantation.

Question 3: What ultrasound finding is the hallmark of anencephaly?

Fluid-filled brain
Enlarged head
Absent cranial vault above the orbits (Correct answer)
Choroid plexus cysts

Correct answer: Absent cranial vault above the orbits

Anencephaly is characterized by complete absence of the cranial vault and cerebral hemispheres above the orbits, resulting in a 'frog-eye' appearance on ultrasound.

Question 4: What is the primary purpose of ultrasound in pregnancy?

To visualize and monitor fetal development (Correct answer)
To determine the mother's health only
To diagnose maternal illnesses
To measure blood pressure

Correct answer: To visualize and monitor fetal development

Ultrasound technology works by emitting high-frequency sound waves into the body. These sound waves bounce off internal structures and return to the machine, which then processes them to create a real-time image. This is distinct from other imaging methods like X-rays or MRI, which use different types of energy.

Question 5: What is the normal fetal heart rate range in the first trimester?

180–220 bpm
50–60 bpm
60–80 bpm
100–170 bpm (Correct answer)

Correct answer: 100–170 bpm

Normal first-trimester fetal heart rates range from approximately 100 to 170 beats per minute, with rates below 100 bpm at 6–8 weeks associated with poor prognosis.

Question 6: During a routine second-trimester anatomy scan, which of the following is NOT typically assessed?

Maternal hormone levels (Correct answer)
Placental location
Cervical length
Fetal organs and skeletal system

Correct answer: Maternal hormone levels

The second-trimester anatomy scan, usually performed between 18-22 weeks, is a detailed examination of the fetus's organs, skeletal system, and overall development, as well as the placenta's location and cervical length. Maternal hormone levels are typically assessed through blood tests, not directly through an ultrasound scan.

Question 7: Why is fetal echocardiography performed during pregnancy?

To evaluate the structure and function of the fetal heart (Correct answer)
To determine fetal viability
To measure fetal heart rate
To check for placental abnormalities

Correct answer: To evaluate the structure and function of the fetal heart

Fetal echocardiography is a specialized ultrasound examination focused specifically on the fetal heart. It is performed to thoroughly evaluate the structure, function, and rhythm of the fetal heart, allowing for the detection and diagnosis of congenital heart defects, which are among the most common birth anomalies.

Question 8: Which type of placenta previa has the highest risk for cesarean delivery?

Low-lying placenta
Complete placenta previa (Correct answer)
Partial placenta previa
Marginal placenta previa

Correct answer: Complete placenta previa

Complete placenta previa, where the placenta entirely covers the internal cervical os, has the highest risk and virtually always requires cesarean delivery.

Question 9: What condition is suggested when all fetal biometric measurements are proportionally small?

Macrosomia
Normal variant
Asymmetric IUGR
Symmetric IUGR (Correct answer)

Correct answer: Symmetric IUGR

When all measurements (BPD, HC, AC, FL) are equally reduced, it suggests symmetric IUGR, often due to early insults such as genetic abnormalities or infections.

Question 10: The cephalic index (CI) is calculated as which ratio?

BPD divided by occipitofrontal diameter × 100 (Correct answer)
AC divided by HC × 100
FL divided by BPD × 100
HC divided by BPD × 100

Correct answer: BPD divided by occipitofrontal diameter × 100

The cephalic index is BPD/OFD × 100 and is used to assess head shape; a normal CI is between 70 and 86.

Question 11: The nuchal translucency (NT) measurement is performed at what gestational age range?

6–8 weeks
8–10 weeks
15–20 weeks
11–14 weeks (CRL 45–84 mm) (Correct answer)

Correct answer: 11–14 weeks (CRL 45–84 mm)

NT measurement is performed between 11+0 and 13+6 weeks gestation, when the CRL is between 45 and 84 mm, for first-trimester Down syndrome screening.

Question 12: Which formula specifically accounts for asymmetric head shape when estimating gestational age?

FL-based formula
HC-based formula (Correct answer)
AC-based formula
BPD-based formula

Correct answer: HC-based formula

Head circumference-based formulas are preferred over BPD-based formulas because HC is not affected by fetal head shape variations.

Question 13: A fetus measuring below which percentile is typically classified as small for gestational age (SGA)?

5th percentile
15th percentile
25th percentile
10th percentile (Correct answer)

Correct answer: 10th percentile

A fetus with an estimated weight below the 10th percentile for gestational age is classified as small for gestational age (SGA).

Question 14: What is the normal range for amniotic fluid index (AFI) in a term pregnancy?

1–5 cm
25–35 cm
2–6 cm
8–24 cm (Correct answer)

Correct answer: 8–24 cm

A normal AFI at term ranges from 8 to 24 cm; values below 5 cm indicate oligohydramnios and above 24 cm indicate polyhydramnios.

Question 15: What does an echogenic intracardiac focus (EIF) represent on ultrasound?

Cardiac tumor
Pericardial effusion
A calcification in the papillary muscle, a soft marker for aneuploidy (Correct answer)
A ventricular septal defect

Correct answer: A calcification in the papillary muscle, a soft marker for aneuploidy

An EIF is a bright spot in the fetal heart representing a calcification of the papillary muscle and is considered a soft marker for chromosomal abnormalities, particularly Trisomy 21.

Question 16: What is the cerebroplacental ratio (CPR) and why is it significant?

MCA velocity divided by UA velocity
MCA PI plus UA PI
MCA PI divided by UA PI; low CPR indicates brain-sparing and fetal compromise (Correct answer)
UA PI divided by MCA PI

Correct answer: MCA PI divided by UA PI; low CPR indicates brain-sparing and fetal compromise

The CPR is calculated as MCA PI divided by UA PI; a ratio below 1.0 indicates brain-sparing (redistribution) and is associated with adverse perinatal outcomes.

Question 17: Serial ultrasound exams to monitor fetal growth are typically performed how far apart?

Every week
Every 3–4 weeks (Correct answer)
Daily
Every 6–8 weeks

Correct answer: Every 3–4 weeks

Serial growth scans are typically scheduled every 3 to 4 weeks, as shorter intervals do not allow enough time to detect meaningful growth changes.

Question 18: What is the appropriate protocol for measuring fetal heart rate during an obstetric ultrasound?

Visually estimate the rate during real-time imaging.
Measure the heart rate using M-mode ultrasound. (Correct answer)
Use Doppler ultrasound for continuous monitoring throughout the scan.
Record fetal heart sounds with a stethoscope.

Correct answer: Measure the heart rate using M-mode ultrasound.

M-mode ultrasound is a specific display mode that shows the movement of structures over time along a single line. It is particularly useful for accurately measuring the fetal heart rate by tracking the movement of the heart valves or walls, providing a precise numerical value. Doppler ultrasound is used for blood flow, not typically for heart rate measurement in this context.

Question 19: What defines Quintero Stage II in twin-to-twin transfusion syndrome (TTTS)?

Hydrops in the recipient twin
Fetal demise of one or both twins
Absent or reversed end-diastolic flow in the umbilical artery
Oligohydramnios-polyhydramnios sequence with an absent donor bladder (Correct answer)

Correct answer: Oligohydramnios-polyhydramnios sequence with an absent donor bladder

Stage II is characterized by the TOPS sequence progressing to the point where the donor's bladder is no longer visible due to oliguria from severe volume depletion.

Question 20: Twin anemia-polycythemia sequence (TAPS) is best identified on ultrasound by which Doppler finding?

Elevated umbilical vein pulsatility index
Reversed a-wave in the ductus venosus of the polycythemic twin
Middle cerebral artery peak systolic velocity (MCA-PSV) >1.5 MoM in the anemic twin (Correct answer)
Absent end-diastolic flow in the donor twin's umbilical artery

Correct answer: Middle cerebral artery peak systolic velocity (MCA-PSV) >1.5 MoM in the anemic twin

MCA-PSV >1.5 MoM is the standard Doppler marker for fetal anemia; in TAPS the donor becomes anemic, and this finding distinguishes TAPS from TTTS.

Question 21: What does absent end-diastolic flow (AEDF) in the umbilical artery indicate?

Mild IUGR only
Normal placental function
Polyhydramnios
Severely elevated placental resistance with high risk of fetal compromise (Correct answer)

Correct answer: Severely elevated placental resistance with high risk of fetal compromise

Absent end-diastolic flow in the umbilical artery indicates markedly elevated placental vascular resistance and is associated with severe fetal compromise and increased perinatal mortality.

Question 22: Which complication is unique to monochorionic-monoamniotic twins and is responsible for their significantly elevated perinatal mortality risk?

Increased risk of placenta previa due to large shared placenta
Discordant growth leading to selective IUGR
Umbilical cord entanglement causing acute fetal compromise or demise (Correct answer)
Twin-to-twin transfusion syndrome causing hydrops

Correct answer: Umbilical cord entanglement causing acute fetal compromise or demise

Cord entanglement occurs in virtually all MCMA pregnancies and poses a persistent risk of sudden fetal death from acute cord compression, driving the high perinatal mortality rate.

Question 23: In dichorionic-diamniotic twins, what is the typical appearance of the inter-twin membrane at the 11–14 week scan?

A very thin single-layer membrane with a T-sign at placental insertion
A membrane showing the T-sign on one side and lambda sign on the other
No visible membrane in the first trimester
A thick membrane with a wedge of placental tissue (lambda sign) at its insertion (Correct answer)

Correct answer: A thick membrane with a wedge of placental tissue (lambda sign) at its insertion

The lambda (twin peak) sign in DCDA twins is formed by chorionic villi invading the base of the thick inter-twin membrane, creating a triangular echogenic wedge.

Question 24: What finding on ultrasound is characteristic of a circumvallate placenta?

Rolled or raised placental edges with membrane insertion inward from the edge (Correct answer)
Calcified placental edges
Placenta covering the cervix
Abnormal cord insertion

Correct answer: Rolled or raised placental edges with membrane insertion inward from the edge

A circumvallate placenta has membranes that insert inside the placental edge rather than at the periphery, creating a raised rim around the placenta on ultrasound.

Question 25: Which marker on second-trimester ultrasound is associated with Down syndrome (Trisomy 21)?

Enlarged cerebellum
Thick corpus callosum
Absent or hypoplastic nasal bone (Correct answer)
Large thymus

Correct answer: Absent or hypoplastic nasal bone

An absent or hypoplastic nasal bone is one of the soft markers for Down syndrome identified on second-trimester ultrasound.

Question 26: What is the brain-sparing effect in Doppler assessment?

Decreased MCA flow with normal UA flow
Normal MCA and UA flow
Increased MCA flow with decreased umbilical artery flow indicating redistribution to protect the brain (Correct answer)
Equal MCA and UA resistance

Correct answer: Increased MCA flow with decreased umbilical artery flow indicating redistribution to protect the brain

Brain-sparing refers to vasodilation of the middle cerebral artery with reduced resistance, allowing more blood to reach the fetal brain when placental insufficiency is present.

Question 27: What condition is most commonly evaluated using Doppler ultrasound in high-risk pregnancies?

Amniotic fluid infections
Cervical length insufficiency
Maternal hydration
Fetal growth restriction (FGR) and placental insufficiency (Correct answer)

Correct answer: Fetal growth restriction (FGR) and placental insufficiency

Doppler ultrasound is essential in high-risk pregnancies because it can non-invasively assess blood flow in various fetal and maternal vessels, such as the umbilical artery and middle cerebral artery. This helps detect conditions like fetal growth restriction (FGR) and placental insufficiency, where inadequate blood flow can compromise fetal oxygen and nutrient supply.

Question 28: Selective intrauterine growth restriction (sIUGR) in monochorionic twins is primarily defined by which finding?

EFW discordance >20% with normal umbilical artery Dopplers
Polyhydramnios developing in the larger twin's sac
EFW of one twin below the 10th percentile for gestational age (Correct answer)
EFW discordance >10% with abnormal Dopplers in the smaller twin

Correct answer: EFW of one twin below the 10th percentile for gestational age

sIUGR is defined as EFW below the 10th percentile in one monochorionic twin, distinguishing it from TTTS which requires the oligohydramnios-polyhydramnios sequence.

Question 29: What is typically assessed in the maternal ovaries during an ultrasound?

Hormone levels
Presence of cysts or other abnormalities (Correct answer)
The number of eggs
Fetal development

Correct answer: Presence of cysts or other abnormalities

While the primary focus of obstetric ultrasound is the fetus and uterus, the maternal ovaries are often visualized to check for any cysts, masses, or other abnormalities that could potentially complicate the pregnancy or require monitoring. This ensures a comprehensive assessment of the maternal pelvic organs.

Question 30: What is gastroschisis?

Herniation of organs through the umbilical cord
A defect with a membrane covering the organs
A defect in the abdominal wall to the right of the umbilicus with herniated bowel (Correct answer)
A covered midline abdominal wall defect containing liver

Correct answer: A defect in the abdominal wall to the right of the umbilicus with herniated bowel

Gastroschisis is a paraumbilical abdominal wall defect, usually to the right of the cord, through which bowel herniates freely without a covering membrane.

Question 31: What does IUGR stand for in obstetric ultrasound?

Internal Uterine Growth Rate
Integrated Uterine Growth Response
Intrauterine Growth Restriction (Correct answer)
Intrauterine Gestational Ratio

Correct answer: Intrauterine Growth Restriction

IUGR (Intrauterine Growth Restriction) refers to a condition where the fetus does not grow at the expected rate inside the womb.

Question 32: When measuring nuchal translucency (NT) in a twin pregnancy, how should the measurement be performed?

Each twin's NT is measured independently and compared to singleton reference ranges (Correct answer)
Only the larger twin's NT is measured to avoid redundancy
A single combined NT value is calculated for the pair
Add 2 mm to each twin's individual measurement as a twin correction factor

Correct answer: Each twin's NT is measured independently and compared to singleton reference ranges

Each twin's NT is measured independently using the same singleton reference ranges, as NT performance for aneuploidy screening has been validated using this approach.

Question 33: What is the S/D ratio in umbilical artery Doppler?

The ratio of diastolic to systolic velocity
The ratio of systolic to mean velocity
The ratio of peak systolic to end-diastolic velocity (Correct answer)
The pulsatility index

Correct answer: The ratio of peak systolic to end-diastolic velocity

The S/D ratio (systolic-to-diastolic ratio) compares peak systolic velocity to end-diastolic velocity in the umbilical artery and reflects placental vascular resistance.

Question 34: Which ultrasound finding is associated with placenta accreta spectrum?

Placenta in the fundus
Bilobed placenta
Thick placenta over 5 cm
Loss of the retroplacental hypoechoic zone (Correct answer)

Correct answer: Loss of the retroplacental hypoechoic zone

Loss of the normal retroplacental hypoechoic (clear) zone between the placenta and myometrium is a key ultrasound sign of placenta accreta.

Question 35: Which type of waves does an ultrasound machine use to create images?

Sound waves (Correct answer)
X-rays
Light waves
Gamma rays

Correct answer: Sound waves

The transducer is the handheld device that an sonographer places on the patient's skin. It contains piezoelectric crystals that convert electrical energy into sound waves and then convert the returning echoes back into electrical signals, which are used to form the ultrasound image. It is the core component for image acquisition.

Question 36: What is the term for the part of the ultrasound machine that emits and receives sound waves?

Probe
Transducer (Correct answer)
Monitor
Amplifier

Correct answer: Transducer

The frequency of ultrasound waves affects image resolution and penetration depth. In obstetric imaging, a range of 2-12 MHz is typically used because it provides a good balance, allowing for sufficient penetration to visualize the fetus while maintaining adequate image detail for diagnostic purposes. Higher frequencies offer better resolution but less penetration, while lower frequencies penetrate deeper but with less detail.

Question 37: Which measurement is considered the most accurate indicator of gestational age in the second trimester?

Femur length (FL)
Biparietal diameter (BPD) (Correct answer)
Abdominal circumference (AC)
Head circumference (HC)

Correct answer: Biparietal diameter (BPD)

The biparietal diameter is the most widely used and reliable measurement for estimating gestational age in the second trimester.

Question 38: What Doppler finding in the umbilical vein is associated with severe cardiac compromise?

Pulsatile umbilical venous flow (Correct answer)
High velocity flow
Continuous flow
Low velocity flow

Correct answer: Pulsatile umbilical venous flow

Pulsatile (phasic) flow in the normally continuous umbilical venous waveform indicates severe right heart failure and elevated central venous pressure in the fetus.

Question 39: What is the purpose of plotting fetal measurements on growth curves?

To calculate the mother's BMI
To assess amniotic fluid volume
To compare measurements to population norms for gestational age (Correct answer)
To determine placental location

Correct answer: To compare measurements to population norms for gestational age

Growth curves allow sonographers to compare fetal measurements to established population norms, identifying fetuses that fall outside normal ranges for their gestational age.

Question 40: What condition does a 'strawberry-shaped' fetal skull suggest?

Turner syndrome
Trisomy 13 (Patau syndrome)
Trisomy 18 (Edwards syndrome) (Correct answer)
Trisomy 21 (Down syndrome)

Correct answer: Trisomy 18 (Edwards syndrome)

A strawberry-shaped skull, with flattening of the occiput and pointed frontal bones, is a classic cranial marker associated with Trisomy 18.

Question 41: What does a single umbilical artery (SUA) indicate?

Always associated with IUGR
Normal variant with no clinical significance
An association with chromosomal and structural anomalies (Correct answer)
Indicates placenta previa

Correct answer: An association with chromosomal and structural anomalies

A single umbilical artery (two-vessel cord) is associated with an increased risk of chromosomal abnormalities, structural anomalies, and IUGR compared to a normal three-vessel cord.

Question 42: What is the earliest structure visualized on transvaginal ultrasound in a normal intrauterine pregnancy?

Fetal pole
Yolk sac
Gestational sac (Correct answer)
Fetal heartbeat

Correct answer: Gestational sac

The gestational sac is the earliest structure visible on transvaginal ultrasound, typically seen by 4.5 to 5 weeks of gestation as a small anechoic structure within the decidua.

Question 43: A hyperechoic bowel finding on second-trimester ultrasound may indicate which condition?

Cystic fibrosis, Down syndrome, or cytomegalovirus infection (Correct answer)
Normal variant only
Gastroschisis
Duodenal atresia

Correct answer: Cystic fibrosis, Down syndrome, or cytomegalovirus infection

Echogenic bowel (bowel as bright as bone) is a soft marker associated with cystic fibrosis, Down syndrome, CMV infection, and fetal swallowing of blood.

Question 44: When counting membrane layers to confirm chorionicity, how many layers does a dichorionic-diamniotic inter-twin membrane contain?

3 layers (two amnions and one chorion)
4 layers (two amnions and two chorions) (Correct answer)
2 layers (one amnion from each twin)
1 layer (fused amnion)

Correct answer: 4 layers (two amnions and two chorions)

A DCDA inter-twin membrane has four layers: two amnions (one per twin) and two chorions (one per twin), producing a thick membrane visible on ultrasound.

Question 45: At what gestational age is crown-rump length (CRL) the most accurate dating tool?

After 28 weeks
20–28 weeks
6–12 weeks (Correct answer)
13–20 weeks

Correct answer: 6–12 weeks

Crown-rump length measurement is most accurate for gestational dating between 6 and 12 weeks, with an accuracy of ±3–5 days.

Question 46: What does an elevated pulsatility index (PI) in the uterine artery suggest in early pregnancy?

Normal placental development
Increased risk of preeclampsia and IUGR (Correct answer)
Fetal anemia
Placenta previa

Correct answer: Increased risk of preeclampsia and IUGR

An elevated uterine artery PI in the first or second trimester, especially with a diastolic notch, indicates impaired trophoblastic invasion and raises the risk of preeclampsia and IUGR.

Question 47: Which layer of the uterus is responsible for its contraction during labor?

Decidua
Myometrium (Correct answer)
Endometrium
Perimetrium

Correct answer: Myometrium

The myometrium is the thick, muscular middle layer of the uterine wall. It is composed of smooth muscle fibers that are responsible for the powerful contractions during labor, which help to push the baby out of the uterus. The other layers have different functions, such as the endometrium lining the cavity and the perimetrium forming the outer covering.

Question 48: What is the significance of an abdominal circumference crossing two major percentile lines downward on a growth chart?

It indicates polyhydramnios
It confirms fetal macrosomia
It suggests developing IUGR requiring further evaluation (Correct answer)
It is a normal variation

Correct answer: It suggests developing IUGR requiring further evaluation

A downward crossing of two major percentile lines on a growth chart indicates decelerating fetal growth, which is a significant finding requiring further assessment.

Question 49: How is the maternal bladder relevant during an early pregnancy ultrasound?

A full bladder helps improve visualization of pelvic structures. (Correct answer)
It provides nutrients to the uterus.
It stores hormones for the fetus.
It is used to measure fetal urine output.

Correct answer: A full bladder helps improve visualization of pelvic structures.

In early pregnancy, especially during transabdominal ultrasounds, a full maternal bladder is often required. The fluid-filled bladder acts as an acoustic window, pushing the uterus and other pelvic structures into a more favorable position and improving the transmission of sound waves, which enhances the visualization of the early gestational sac and embryo.

Question 50: Which ultrasound finding best distinguishes dichorionic-diamniotic (DCDA) twins from monochorionic-diamniotic (MCDA) twins in the first trimester?

Crown-rump length discordance greater than 5 days
Twin peak (lambda) sign at placental insertion (Correct answer)
Presence of any dividing membrane
Number of yolk sacs visible

Correct answer: Twin peak (lambda) sign at placental insertion

The lambda (twin peak) sign represents chorionic villi extending into the base of the inter-twin membrane, indicating dichorionic placentation.

Question 51: What is the purpose of color Doppler in placental evaluation?

To grade placental maturity
To count placental lobules
To measure placental thickness
To identify abnormal vascularity and flow patterns suggesting accreta (Correct answer)

Correct answer: To identify abnormal vascularity and flow patterns suggesting accreta

Color Doppler helps identify abnormal vascular patterns within the placenta and myometrium, which are key findings in diagnosing placenta accreta spectrum.

Question 52: At what gestational age is it recommended to perform a detailed fetal anatomy scan?

18–22 weeks (Correct answer)
12–14 weeks
8–10 weeks
28–32 weeks

Correct answer: 18–22 weeks

The detailed fetal anatomy scan is a crucial ultrasound performed between 18 and 22 weeks of gestation. At this stage, the fetal organs are sufficiently developed and large enough to be clearly visualized and assessed for any structural abnormalities or developmental issues. This timing allows for early detection and management planning if necessary.

Question 53: What does placental grading assess on ultrasound?

Placental thickness
Placental weight
Placental blood flow
Placental maturity based on echogenicity and calcifications (Correct answer)

Correct answer: Placental maturity based on echogenicity and calcifications

Placental grading (Grannum classification) assesses maturity by evaluating echogenicity patterns, calcifications, and basal layer changes on ultrasound.

Question 54: What is the banana sign in fetal ultrasound?

Curved spine in scoliosis
Bent femur appearance
Curved shape of the cerebellum due to hindbrain herniation in spina bifida (Correct answer)
Banana-shaped kidney

Correct answer: Curved shape of the cerebellum due to hindbrain herniation in spina bifida

The banana sign describes the abnormal curved shape of the cerebellum caused by caudal displacement of the hindbrain through the foramen magnum (Chiari II malformation) in open spina bifida.

Question 55: In a naturally conceived triplet pregnancy, what is the most common chorionicity-amnionicity configuration?

Monochorionic-triamniotic
Monochorionic-diamniotic plus one dichorionic sac
Dichorionic-triamniotic
Trichorionic-triamniotic (Correct answer)

Correct answer: Trichorionic-triamniotic

Spontaneous triplets arise from three separately ovulated and fertilized eggs in the vast majority of cases, resulting in trichorionic-triamniotic placentation.

Question 56: At what gestational age does the placenta normally migrate away from the cervical os?

At 16 weeks
By 28–32 weeks as the lower uterine segment develops (Correct answer)
After 36 weeks
At 20 weeks

Correct answer: By 28–32 weeks as the lower uterine segment develops

As the lower uterine segment elongates between 28 and 32 weeks, a low-lying placenta may appear to move away from the cervical os, a process called placental migration.

Question 57: Which measurement is most affected by fetal head shape variations such as dolichocephaly?

Head circumference (HC)
Abdominal circumference (AC)
Femur length (FL)
Biparietal diameter (BPD) (Correct answer)

Correct answer: Biparietal diameter (BPD)

BPD can be falsely low in dolichocephaly (elongated head) or falsely high in brachycephaly, making HC a more reliable measurement in these cases.

Question 58: What is a pseudogestational sac in the context of ectopic pregnancy?

A fluid collection within the uterine cavity caused by ectopic hCG stimulation, mimicking a gestational sac (Correct answer)
A cornual pregnancy sac
A subchorionic hemorrhage
A twin gestational sac

Correct answer: A fluid collection within the uterine cavity caused by ectopic hCG stimulation, mimicking a gestational sac

A pseudogestational sac is a centrally located fluid collection in the uterine cavity caused by decidual reaction from an ectopic pregnancy, and lacks the double echogenic ring of a true sac.

Question 59: Which ultrasound finding is associated with congenital diaphragmatic hernia (CDH)?

Hyperechoic lung mass
Absent stomach bubble
Stomach and bowel in the chest alongside the heart (Correct answer)
Pericardial effusion

Correct answer: Stomach and bowel in the chest alongside the heart

In CDH, abdominal organs herniate through a diaphragmatic defect into the chest, causing the stomach and bowel to appear alongside or displacing the heart.

Question 60: What is the purpose of uterine artery Doppler screening at 20–24 weeks?

To assess fetal position
To diagnose placenta previa
To predict preeclampsia and placental insufficiency later in pregnancy (Correct answer)
To measure cervical length

Correct answer: To predict preeclampsia and placental insufficiency later in pregnancy

Uterine artery Doppler at 20 to 24 weeks is used to identify women with persistently elevated resistance, predicting risk for subsequent preeclampsia and uteroplacental insufficiency.

Question 61: Why is the maternal uterus assessed during pregnancy ultrasounds?

To monitor fetal development and placental health (Correct answer)
To evaluate pelvic bone structure
To detect maternal infections
To measure maternal hormone levels

Correct answer: To monitor fetal development and placental health

The maternal uterus is the organ that houses and nourishes the developing fetus throughout pregnancy. Assessing it during ultrasound is crucial for monitoring fetal growth, position, and overall well-being, as well as evaluating the health and location of the placenta, which provides vital nutrients and oxygen to the baby.

Question 62: What is a subchorionic hemorrhage (SCH) on first-trimester ultrasound?

Blood within the gestational sac
A collection of blood between the gestational sac and the uterine wall (Correct answer)
Placental abruption
Hemorrhage within the embryo

Correct answer: A collection of blood between the gestational sac and the uterine wall

An SCH is a crescent-shaped collection of blood between the chorionic membrane of the gestational sac and the uterine wall, associated with an increased risk of miscarriage.

Question 63: Peak systolic velocity (PSV) in the middle cerebral artery is used to diagnose which fetal condition?

Fetal anemia (Correct answer)
Ventriculomegaly
Placenta accreta
IUGR

Correct answer: Fetal anemia

MCA PSV greater than 1.5 multiples of the median (MoM) for gestational age is the standard non-invasive method to screen for fetal anemia.

Question 64: What does the pulsatility index (PI) calculation include that the S/D ratio does not?

Angle correction
Mean velocity in the denominator (Correct answer)
End-diastolic velocity
Peak systolic velocity

Correct answer: Mean velocity in the denominator

The PI is calculated as (systolic minus diastolic) divided by mean velocity, making it usable even when end-diastolic flow is absent or reversed, unlike the S/D ratio.

Question 65: Nuchal fold thickness greater than how many millimeters at 16–20 weeks is considered abnormal?

10 mm
8 mm
6 mm (Correct answer)
4 mm

Correct answer: 6 mm

A nuchal fold thickness of 6 mm or greater measured at 16 to 20 weeks gestation is considered an abnormal finding and a soft marker for Down syndrome.

Question 66: What does the resistance index (RI) measure in Doppler assessment?

Diastolic / Systolic velocity
Mean velocity / Systolic velocity
Systolic velocity alone
(Systolic - Diastolic) / Systolic velocity (Correct answer)

Correct answer: (Systolic - Diastolic) / Systolic velocity

The resistance index is calculated as (systolic minus diastolic velocity) divided by systolic velocity, providing a measure of vascular resistance that is independent of the angle of insonation.

Question 67: What is the recommended timing of the first ultrasound to optimally determine chorionicity in a newly diagnosed twin pregnancy?

As early as possible, ideally before 14 weeks of gestation (Correct answer)
At 16–18 weeks when the membrane is thicker and easier to count
At the 18–20 week anatomy scan combined with anomaly screening
Any time during the first half of pregnancy is equally reliable

Correct answer: As early as possible, ideally before 14 weeks of gestation

Chorionicity should be determined before 14 weeks because the lambda and T-signs are most reliable in the first trimester and become harder to distinguish as pregnancy advances.

Question 68: A bilobed placenta differs from a succenturiate lobe in that:

One lobe is much smaller than the other
The cord inserts in the larger lobe only
The lobes are not connected by vessels
Both lobes are approximately equal in size (Correct answer)

Correct answer: Both lobes are approximately equal in size

A bilobed (bipartite) placenta has two roughly equal-sized lobes connected by membranes and vessels, whereas a succenturiate lobe is clearly smaller than the main placenta.

Question 69: What does an increased nuchal translucency (NT ≥3.5 mm) indicate?

Increased risk of chromosomal abnormalities, cardiac defects, and genetic syndromes (Correct answer)
Confirms Down syndrome diagnosis
Only indicates Turner syndrome
Normal first-trimester finding

Correct answer: Increased risk of chromosomal abnormalities, cardiac defects, and genetic syndromes

An NT of 3.5 mm or greater is associated with significantly increased risk of trisomies (21, 18, 13), Turner syndrome, cardiac defects, and various genetic syndromes.

Question 70: What is the mean sac diameter (MSD)?

The length of the sac only
The width of the sac only
The average of three perpendicular measurements of the gestational sac (Correct answer)
The sac measurement minus the yolk sac

Correct answer: The average of three perpendicular measurements of the gestational sac

MSD is calculated by averaging three perpendicular internal measurements (length, width, height) of the gestational sac and is used to assess early pregnancy development.

Question 71: Which cardiac abnormality is most commonly detected on the four-chamber view of the fetal heart?

Hypoplastic left heart syndrome (Correct answer)
Tetralogy of Fallot
Transposition of the great arteries
Coarctation of the aorta

Correct answer: Hypoplastic left heart syndrome

Hypoplastic left heart syndrome causes marked asymmetry of the cardiac chambers, making it the most commonly detected cardiac defect on the four-chamber view.

Question 72: What is the lemon sign associated with?

Spina bifida/open neural tube defect (Correct answer)
Anencephaly
Holoprosencephaly
Hydrocephalus

Correct answer: Spina bifida/open neural tube defect

The lemon sign refers to scalloping of the frontal bones giving the skull a lemon shape and is a classic second-trimester marker for open spina bifida.

Question 73: Acardiac twinning (twin reversed arterial perfusion — TRAP sequence) occurs exclusively in which type of twin pregnancy?

Monochorionic-monoamniotic twins only
Monochorionic-diamniotic twins only
Dichorionic-diamniotic twins only
Any monochorionic twin pregnancy regardless of amnionicity (Correct answer)

Correct answer: Any monochorionic twin pregnancy regardless of amnionicity

TRAP sequence requires arterio-arterial anastomoses within a shared monochorionic placenta, so it can occur in any monochorionic pregnancy (MCDA or MCMA).

Question 74: At what beta-hCG level should a gestational sac be visible on transvaginal ultrasound?

1,500–2,000 mIU/mL (Correct answer)
500 mIU/mL
5,000 mIU/mL
10,000 mIU/mL

Correct answer: 1,500–2,000 mIU/mL

A gestational sac should be visible on transvaginal ultrasound when serum beta-hCG reaches approximately 1,500 to 2,000 mIU/mL; failure to visualize raises concern for ectopic pregnancy.

Question 75: Choroid plexus cysts (CPCs) are most strongly associated with which chromosomal abnormality?

Trisomy 13
Monosomy X
Trisomy 21
Trisomy 18 (Correct answer)

Correct answer: Trisomy 18

While CPCs can be a normal variant, when found in combination with other structural abnormalities, they are most strongly associated with Trisomy 18.

Question 76: What finding on first-trimester ultrasound is most suggestive of a failed pregnancy (missed abortion)?

CRL ≥7 mm with no cardiac activity on transvaginal scan (Correct answer)
Single umbilical artery
Anterior placenta
Small gestational sac

Correct answer: CRL ≥7 mm with no cardiac activity on transvaginal scan

Per ACOG/SRU criteria, a CRL of 7 mm or greater with no visible cardiac activity on transvaginal ultrasound is diagnostic of embryonic demise.

Question 77: Where is the placenta most commonly located in uncomplicated pregnancies?

Fundus
Anterior uterine wall
Lower uterine segment
Posterior uterine wall (Correct answer)

Correct answer: Posterior uterine wall

The placenta most commonly implants on the posterior uterine wall, though anterior and fundal implantation are also normal locations.

Question 78: At what atrial width measurement is ventriculomegaly diagnosed?

Greater than 12 mm
Greater than 15 mm
Greater than 10 mm (Correct answer)
Greater than 8 mm

Correct answer: Greater than 10 mm

Ventriculomegaly is diagnosed when the atrium of the lateral ventricle measures greater than 10 mm; measurements between 10–15 mm are mild and above 15 mm are severe.

Question 79: In ultrasound surveillance of multiple gestations, discordant growth is standardly defined as an estimated fetal weight difference exceeding what threshold?

Greater than 20% based on estimated fetal weight of the larger twin (Correct answer)
Greater than 25% based on femur length discrepancy
Greater than 5% based on abdominal circumference measurements
Greater than 10% based on biparietal diameter

Correct answer: Greater than 20% based on estimated fetal weight of the larger twin

A >20% EFW discordance (calculated as [larger EFW − smaller EFW] ÷ larger EFW × 100) is the accepted clinical threshold for significant growth discordance in multiple gestations.

Question 80: What is the most common cause of ventriculomegaly detected on prenatal ultrasound?

Neural tube defect
Aqueductal stenosis (Correct answer)
Infection
Chromosomal abnormality

Correct answer: Aqueductal stenosis

Aqueductal stenosis, which obstructs CSF flow between the third and fourth ventricles, is the most common cause of isolated congenital ventriculomegaly.

Question 81: What is macrosomia defined as in ultrasound practice?

Femur length above normal limits
Estimated fetal weight above the 75th percentile
Estimated fetal weight above the 90th percentile (Correct answer)
Birth weight over 3,000 grams

Correct answer: Estimated fetal weight above the 90th percentile

Macrosomia is defined as an estimated fetal weight above the 90th percentile for gestational age, or commonly above 4,000–4,500 grams at term.

Question 82: What is polyhydramnios defined as using the AFI?

AFI greater than 24 cm (Correct answer)
AFI greater than 30 cm
AFI greater than 20 cm
AFI greater than 18 cm

Correct answer: AFI greater than 24 cm

Polyhydramnios is diagnosed when the AFI exceeds 24 cm, indicating excess amniotic fluid that may be associated with fetal anomalies or maternal diabetes.

Question 83: What is a succenturiate lobe of the placenta?

A marginal placenta previa
An accessory placental lobe separate from the main placenta (Correct answer)
A placenta with calcifications
A placenta with a velamentous cord insertion

Correct answer: An accessory placental lobe separate from the main placenta

A succenturiate lobe is an accessory lobe of placental tissue connected to the main placenta by blood vessels running through the membranes.

Question 84: What is the role of the cervix during pregnancy?

It facilitates the production of amniotic fluid.
It maintains pregnancy by remaining closed and shortens during labor. (Correct answer)
It nourishes the fetus.
It supports fetal blood flow.

Correct answer: It maintains pregnancy by remaining closed and shortens during labor.

During pregnancy, the cervix plays a critical role in maintaining the pregnancy by remaining long and closed, forming a protective barrier for the fetus. As labor approaches, the cervix begins to soften, shorten (efface), and open (dilate) to allow the baby to pass through the birth canal. Its integrity is vital for preventing preterm birth.

Question 85: What is the significance of a large-for-dates gestational sac (MSD > 25 mm) with no visible embryo?

Twin pregnancy
Hydatidiform mole
Anembryonic pregnancy (blighted ovum) (Correct answer)
Normal early pregnancy

Correct answer: Anembryonic pregnancy (blighted ovum)

Per ACOG criteria, a gestational sac with MSD ≥25 mm and no visible embryo on transvaginal ultrasound is diagnostic of an anembryonic pregnancy.

Question 86: The 'stuck twin' appearance on ultrasound in TTTS refers to which specific finding?

One twin showing absent cardiac motion
The donor twin tightly wrapped against the uterine wall due to severe oligohydramnios (Correct answer)
Twins whose bodies appear fused on imaging
One twin fixed in a persistent transverse lie

Correct answer: The donor twin tightly wrapped against the uterine wall due to severe oligohydramnios

The stuck twin is the TTTS donor, whose severely reduced amniotic fluid causes it to be pressed tightly against the uterine wall, appearing 'stuck' without room to move.

Question 87: When is magnetic resonance imaging (MRI) recommended during pregnancy?

When ultrasound findings are inconclusive, particularly for fetal brain or spine abnormalities (Correct answer)
To monitor maternal hormone levels
Routine imaging for every pregnancy
To replace Doppler studies

Correct answer: When ultrasound findings are inconclusive, particularly for fetal brain or spine abnormalities

Magnetic Resonance Imaging (MRI) is a powerful imaging modality that provides excellent soft tissue contrast without using ionizing radiation. It is typically reserved for cases where ultrasound findings are inconclusive or when more detailed information is needed, particularly for complex fetal anomalies involving the brain or spine, due to its superior resolution for these structures.

Question 88: Which vessel is sampled in the ductus venosus Doppler assessment?

The umbilical artery
The aorta
The fetal venous connection between the portal vein and inferior vena cava (Correct answer)
The main portal vein

Correct answer: The fetal venous connection between the portal vein and inferior vena cava

The ductus venosus is a small venous shunt connecting the umbilical vein to the inferior vena cava, bypassing the fetal liver, and is sampled to assess cardiac preload.

Question 89: What is the standard frequency range of ultrasound waves used in obstetric imaging?

2-12 MHz (Correct answer)
50-100 MHz
15-30 MHz
1-5 MHz

Correct answer: 2-12 MHz

The Doppler function in ultrasound utilizes the Doppler effect, which measures changes in the frequency of sound waves as they reflect off moving objects. In medical imaging, this is primarily used to detect and evaluate blood flow within vessels, such as the umbilical cord or fetal heart, providing crucial information about circulation and potential issues like fetal growth restriction.

Question 90: What is an omphalocele?

A midline abdominal wall defect with herniation of organs covered by a membrane (Correct answer)
A bladder exstrophy
A diaphragmatic hernia
A right-sided defect with free bowel herniation

Correct answer: A midline abdominal wall defect with herniation of organs covered by a membrane

An omphalocele is a midline defect at the umbilical cord insertion where abdominal organs herniate into the base of the cord, covered by a peritoneal/amniotic membrane.

Question 91: The 'T-sign' on ultrasound at the placental insertion of the inter-twin membrane is associated with which type of twin placentation?

Monochorionic-diamniotic (Correct answer)
Dichorionic-monoamniotic
Monochorionic-monoamniotic
Dichorionic-diamniotic

Correct answer: Monochorionic-diamniotic

The T-sign occurs in monochorionic-diamniotic twins because the thin membrane inserts perpendicularly into the placenta without chorionic villi filling the base.

Question 92: What is vasa previa?

Low-lying placenta with cord insertion
A placenta covering the cervix
Umbilical cord prolapse
Fetal blood vessels crossing the internal os unprotected by placenta or cord (Correct answer)

Correct answer: Fetal blood vessels crossing the internal os unprotected by placenta or cord

Vasa previa occurs when fetal blood vessels run through the membranes across the internal cervical os, posing a life-threatening risk of hemorrhage if ruptured.

Question 93: What is the primary purpose of 3D/4D ultrasounds in advanced pregnancy imaging?

To measure amniotic fluid levels
To provide entertainment for parents
To assess placental blood flow
To visualize fetal anatomy in more detail for diagnosing abnormalities (Correct answer)

Correct answer: To visualize fetal anatomy in more detail for diagnosing abnormalities

3D/4D ultrasounds provide multi-dimensional views of the fetus, allowing for a more comprehensive and detailed visualization of fetal anatomy compared to 2D scans. This enhanced detail is particularly valuable for diagnosing complex fetal abnormalities, especially those affecting the face, limbs, or surface structures, aiding in prenatal counseling and management.

Question 94: Which Doppler measurement is used in the biophysical profile scoring?

Uterine artery PI
Doppler findings are not part of the standard biophysical profile (Correct answer)
MCA peak systolic velocity
Umbilical artery S/D ratio

Correct answer: Doppler findings are not part of the standard biophysical profile

The classic biophysical profile (BPP) consists of five components including fetal breathing, movements, tone, amniotic fluid, and NST — Doppler is not a standard BPP component.

Question 95: What is the primary purpose of the first-trimester ultrasound?

To detect placental abnormalities
To confirm pregnancy, estimate gestational age, and check for multiples (Correct answer)
To assess fetal movement and organ development
To measure amniotic fluid levels

Correct answer: To confirm pregnancy, estimate gestational age, and check for multiples

The first-trimester ultrasound is typically performed between 6 and 14 weeks of gestation. Its main objectives are to confirm the presence of a viable pregnancy, accurately estimate the gestational age (due date), and determine if there are multiple fetuses. It also helps to identify potential early complications like ectopic pregnancy.

Question 96: What is the significance of the Doppler function in ultrasound?

It produces 3D images.
It measures amniotic fluid levels.
It detects and evaluates blood flow. (Correct answer)
It enhances image contrast.

Correct answer: It detects and evaluates blood flow.

Doppler ultrasound assesses blood flow in the umbilical cord and fetal vessels to monitor fetal health.

Question 97: What AFI value defines oligohydramnios?

Less than 10 cm
Less than 5 cm (Correct answer)
Less than 15 cm
Less than 8 cm

Correct answer: Less than 5 cm

Oligohydramnios is diagnosed when the amniotic fluid index (AFI) is less than 5 cm, indicating a dangerously low level of amniotic fluid.

Question 98: What is the primary use of cervical ultrasound in advanced pregnancy imaging?

To determine the presence of amniotic fluid infections
To assess the risk of preterm labor by measuring cervical length (Correct answer)
To monitor uterine contractions
To evaluate the fetus's position

Correct answer: To assess the risk of preterm labor by measuring cervical length

Cervical ultrasound is primarily used to measure the length of the cervix during pregnancy. A shortened cervical length is a significant risk factor for preterm labor and delivery. Regular monitoring of cervical length, especially in high-risk pregnancies, allows for timely interventions to prevent or manage preterm birth.

Question 99: Which Doppler waveform is used to assess fetal cerebral blood flow?

Circle of Willis
Anterior cerebral artery
Posterior cerebral artery
Middle cerebral artery (MCA) (Correct answer)

Correct answer: Middle cerebral artery (MCA)

The middle cerebral artery is the standard vessel used to assess fetal cerebral blood flow, particularly for detecting brain-sparing in IUGR and anemia.

Question 100: When is Doppler ultrasound considered safe to use in pregnancy?

When indicated clinically, using the lowest output for the shortest time needed (Correct answer)
Only in the third trimester
Only during non-stress tests
Never before 20 weeks

Correct answer: When indicated clinically, using the lowest output for the shortest time needed

Doppler ultrasound is safe when used for clinically indicated reasons following the ALARA principle, using minimum power output for the minimum time required.

Question 101: What ultrasound finding definitively differentiates monochorionic-monoamniotic (MCMA) twins from monochorionic-diamniotic (MCDA) twins?

Lambda sign present versus absent
Complete absence of any dividing membrane between the twins (Correct answer)
Differing cord insertion sites on the placenta
Presence of the T-sign versus no T-sign

Correct answer: Complete absence of any dividing membrane between the twins

The complete absence of a dividing membrane confirms MCMA twinning, whereas MCDA twins have a thin but identifiable membrane separating their sacs.

Question 102: What is the most common site for an ectopic pregnancy?

Cervix
Ovary
Isthmic portion of the tube
Ampullary portion of the fallopian tube (Correct answer)

Correct answer: Ampullary portion of the fallopian tube

Approximately 70% of ectopic pregnancies implant in the ampullary (widest) portion of the fallopian tube, making it the most common ectopic site.

Question 103: What is the intradecidual sign on early pregnancy ultrasound?

The appearance of a cornual pregnancy
Normal cervical mucus
A small gestational sac embedded eccentrically within the decidua before a double sac is formed (Correct answer)
A sign of miscarriage

Correct answer: A small gestational sac embedded eccentrically within the decidua before a double sac is formed

The intradecidual sign is a small early gestational sac seen embedded off-center within the endometrial decidua, supporting intrauterine implantation before the double sac is clearly visible.

Question 104: What is the normal location for a yolk sac in early pregnancy?

Adjacent to the decidua
Within the gestational sac between the amnion and chorion (Correct answer)
Inside the embryo
Outside the gestational sac

Correct answer: Within the gestational sac between the amnion and chorion

The yolk sac is located within the gestational sac in the chorionic space (between the amnion and chorion) and is the first structure seen inside the sac before the embryo.

Question 105: What is placenta previa?

A placenta that covers or is adjacent to the internal cervical os (Correct answer)
A placenta implanted in the uterine fundus
A calcified placenta in late pregnancy
A placenta with abnormal cord insertion

Correct answer: A placenta that covers or is adjacent to the internal cervical os

Placenta previa occurs when the placenta is implanted in the lower uterine segment, partially or completely covering the internal cervical os.

Question 106: What does a head circumference to abdominal circumference (HC/AC) ratio greater than 1.0 after 36 weeks suggest?

Normal growth
Macrosomia
Asymmetric IUGR (Correct answer)
Symmetric IUGR

Correct answer: Asymmetric IUGR

An HC/AC ratio greater than 1.0 after 36 weeks suggests asymmetric IUGR, where the brain is spared but the liver and abdominal organs are affected.

Question 107: What is the standard recommended ultrasound surveillance interval for uncomplicated monochorionic-diamniotic (MCDA) twin pregnancies to screen for TTTS?

Every 2 weeks starting from 16 weeks of gestation (Correct answer)
Every week starting at 20 weeks
Monthly until 28 weeks then biweekly
Every 4 weeks throughout the second trimester

Correct answer: Every 2 weeks starting from 16 weeks of gestation

MCDA twins require every-2-week ultrasound surveillance beginning at 16 weeks to detect TTTS early, as it most commonly develops between 16 and 26 weeks.

Question 108: Which measurement technique is preferred when the umbilical cord obscures fluid pockets in AFI assessment?

Single deepest pocket (SDP) method (Correct answer)
Placental volume calculation
Fetal bladder volume
Doppler flow measurement

Correct answer: Single deepest pocket (SDP) method

The single deepest pocket method is preferred when cord loops are present, as it measures the largest fluid pocket without cord or fetal parts, minimizing error.

Question 109: Which ultrasound finding is most characteristic and pathognomonic of monochorionic-monoamniotic (MCMA) twins?

Lambda sign at placental insertion
Thin dividing membrane measuring less than 2 mm
Significant estimated fetal weight discordance
Umbilical cord entanglement between the twins (Correct answer)

Correct answer: Umbilical cord entanglement between the twins

Cord entanglement is pathognomonic for MCMA twins because both fetuses share a single amniotic cavity with no membrane separating their cords.

Question 110: When performing a biophysical profile (BPP), which of the following parameters is NOT included?

Placental weight (Correct answer)
Gross fetal body movements
Fetal breathing movements
Amniotic fluid volume

Correct answer: Placental weight

A biophysical profile (BPP) is a prenatal test that assesses fetal well-being by evaluating five parameters: fetal breathing movements, gross fetal body movements, fetal tone, amniotic fluid volume, and a non-stress test (fetal heart rate reactivity). Placental weight is not a component of the standard BPP assessment.

Question 111: What is the single deepest pocket (SDP) method used to evaluate?

Uterine artery blood flow
Fetal weight
Amniotic fluid volume (Correct answer)
Placental thickness

Correct answer: Amniotic fluid volume

The single deepest pocket method measures the largest vertical pocket of amniotic fluid free of fetal parts or umbilical cord to assess amniotic fluid volume.

Question 112: What is a normal umbilical artery S/D ratio in the third trimester?

Greater than 6.0
Less than 5.0
Greater than 4.0
Less than 3.0 (Correct answer)

Correct answer: Less than 3.0

In the third trimester, a normal umbilical artery S/D ratio is generally less than 3.0; higher values indicate elevated placental resistance.

Question 113: Why is transvaginal ultrasound preferred over transabdominal ultrasound in early first-trimester assessment?

It is less uncomfortable
It is safer for the fetus
It shows the whole uterus better
It provides higher resolution and can detect structures 1–2 weeks earlier than transabdominal scanning (Correct answer)

Correct answer: It provides higher resolution and can detect structures 1–2 weeks earlier than transabdominal scanning

Transvaginal ultrasound uses a higher frequency transducer placed closer to the uterus, providing superior resolution and detecting embryonic structures approximately 1 to 2 weeks earlier than transabdominal scanning.

Question 114: A normal placenta at term appears as which grade on the Grannum classification?

Grade IV
Grade III only
All grades are normal
Grade 0 to Grade II (Correct answer)

Correct answer: Grade 0 to Grade II

Placental grades 0 through II are considered normal during term pregnancy, while Grade III may indicate premature maturation.

Question 115: What color Doppler setting adjustment is most important for detecting low-velocity venous flow?

Increasing the PRF
Lowering the color velocity scale (PRF) (Correct answer)
Increasing the transducer frequency
Decreasing the depth

Correct answer: Lowering the color velocity scale (PRF)

Lowering the pulse repetition frequency (PRF/color scale) is essential for visualizing low-velocity venous flow, as too high a scale will not display slow-moving blood.

Question 116: Which fetal measurement best reflects fetal nutrition and soft tissue mass?

Head circumference (HC)
Biparietal diameter (BPD)
Abdominal circumference (AC) (Correct answer)
Femur length (FL)

Correct answer: Abdominal circumference (AC)

The abdominal circumference reflects the size of the liver and subcutaneous fat, making it the best indicator of fetal nutrition.

Question 117: According to the Quintero staging system for TTTS, which finding defines Stage I?

Oligohydramnios in donor and polyhydramnios in recipient with a still-visible donor bladder (Correct answer)
Absent end-diastolic flow in the donor's umbilical artery
Fetal demise of one twin
Hydrops in the recipient twin

Correct answer: Oligohydramnios in donor and polyhydramnios in recipient with a still-visible donor bladder

Quintero Stage I is defined by the oligohydramnios-polyhydramnios sequence (TOPS) with the donor's bladder still visible on ultrasound.

Question 118: At what gestational age can chorionicity be most reliably determined by ultrasound?

20–24 weeks anatomy scan
11–14 weeks (Correct answer)
16–18 weeks
6–7 weeks

Correct answer: 11–14 weeks

The lambda and T-signs are most reliably identified between 11 and 14 weeks, making this the optimal window for chorionicity determination.

Question 119: Reversed end-diastolic flow (REDF) in the umbilical artery is associated with what outcome?

Imminent fetal deterioration requiring urgent delivery consideration (Correct answer)
Mild placental insufficiency
Maternal hypertension only
Normal third-trimester finding

Correct answer: Imminent fetal deterioration requiring urgent delivery consideration

REDF in the umbilical artery indicates critical placental resistance with reverse flow during diastole and is associated with very high perinatal morbidity and mortality, often requiring urgent delivery.

Question 120: Which ultrasound parameter is used to calculate the ponderal index as an indicator of fetal nutrition?

AC and HC
BPD and HC
FL and AC
Estimated fetal weight and femur length (Correct answer)

Correct answer: Estimated fetal weight and femur length

The ponderal index uses estimated fetal weight relative to femur length to assess fetal body proportions and nutritional status.

Question 121: A double bubble sign on fetal ultrasound is diagnostic of which condition?

Esophageal atresia
Gastroschisis
Omphalocele
Duodenal atresia (Correct answer)

Correct answer: Duodenal atresia

The double bubble sign represents the dilated stomach and proximal duodenum separated by the pylorus, which is pathognomonic for duodenal atresia.

Question 122: What ultrasound finding suggests renal agenesis as a cause of oligohydramnios?

Absent or severely abnormal kidneys with no bladder filling (Correct answer)
Hyperechoic kidneys
Enlarged kidneys
Hydronephrosis

Correct answer: Absent or severely abnormal kidneys with no bladder filling

In renal agenesis, the fetal kidneys are absent and the bladder does not fill, leading to severe oligohydramnios due to absent urine production.

Question 123: What does reversed flow in the ductus venosus (DV) indicate?

Normal finding in the third trimester
Umbilical cord compression
Mild placental insufficiency
Severely abnormal cardiac function and imminent fetal deterioration (Correct answer)

Correct answer: Severely abnormal cardiac function and imminent fetal deterioration

Reversed or absent flow in the ductus venosus a-wave indicates elevated cardiac afterload and severe cardiac compromise, signaling imminent fetal deterioration.

Question 124: Which bone is measured to assess femur length (FL) in fetal biometry?

The longest bone in the fetal lower leg
The humerus of the upper arm
The longest bone in the fetal thigh (Correct answer)
The radius of the forearm

Correct answer: The longest bone in the fetal thigh

Femur length is measured along the ossified diaphysis of the femur, the longest bone in the fetal thigh.

Question 125: What structure should always be visualized within a gestational sac before a CRL is measurable?

Amnion
Yolk sac (Correct answer)
Fetal pole
Umbilical cord

Correct answer: Yolk sac

The yolk sac must be visible within the gestational sac before an embryo/CRL is measurable and confirms the sac is a true gestational sac rather than a pseudosac.

Question 126: What is the significance of bilateral renal pyelectasis on a second-trimester scan?

It always indicates severe obstruction
It is a soft marker for Down syndrome and warrants follow-up (Correct answer)
It requires immediate delivery
It confirms vesicoureteral reflux

Correct answer: It is a soft marker for Down syndrome and warrants follow-up

Bilateral renal pyelectasis (mild pelviectasis ≥4 mm AP) is a soft marker for Down syndrome and warrants follow-up to assess for persistent hydronephrosis.

Question 127: Which condition is most commonly associated with polyhydramnios?

Placenta previa
Fetal renal agenesis
Fetal gastrointestinal obstruction (Correct answer)
Twin-to-twin transfusion

Correct answer: Fetal gastrointestinal obstruction

Upper GI tract obstructions such as esophageal or duodenal atresia prevent the fetus from swallowing amniotic fluid, leading to polyhydramnios.

Question 128: In twin pregnancies, what percentage of estimated fetal weight (EFW) discordance between twins is generally considered clinically significant?

Greater than 20% (Correct answer)
Greater than 5%
Greater than 10%
Greater than 30%

Correct answer: Greater than 20%

An EFW discordance exceeding 20% between twins is the widely accepted threshold for clinically significant growth discordance requiring closer surveillance.

Question 129: What crown-rump length (CRL) corresponds to the first detectable fetal cardiac activity?

2–4 mm (approximately 5.5–6 weeks) (Correct answer)
8–10 mm
15 mm
1 mm

Correct answer: 2–4 mm (approximately 5.5–6 weeks)

Fetal cardiac activity is typically first detected on transvaginal ultrasound when the CRL reaches 2 to 4 mm, corresponding to approximately 5.5 to 6 weeks gestation.

Question 130: Twin-to-twin transfusion syndrome (TTTS) occurs exclusively in which type of twin pregnancy?

Monochorionic-diamniotic (Correct answer)
Dichorionic-diamniotic
Monochorionic-monoamniotic
Any dizygotic twin pregnancy

Correct answer: Monochorionic-diamniotic

TTTS requires vascular anastomoses within a shared monochorionic placenta, and diamniotic twins are the most common form in which it is diagnosed and treated.

Question 131: The estimated fetal weight (EFW) formula most commonly used in clinical practice incorporates which measurements?

BPD and AC only
BPD, HC, AC, and FL (Correct answer)
AC and BPD only
HC and FL only

Correct answer: BPD, HC, AC, and FL

The Hadlock formula, which incorporates BPD, HC, AC, and FL, is the most widely used method for estimating fetal weight.

ARDMS Obstetrics and Gynecology (OB/GYN) Specialty Examination

The ARDMS OB/GYN specialty examination certifies diagnostic medical sonographers in obstetric and gynecologic ultrasound, covering pelvic anatomy, first and second/third trimester obstetrics, ultrasound protocols and procedures, and physics instrumentation.

170

Questions

180 min

Time Limit

70%

To Pass

Checking for saved progress...

Exam Rules

You can skip questions and return to them later
Flag questions for review before submitting
No feedback shown until you submit the entire exam
Unanswered questions count as wrong — answer everything
10 pretest questions are mixed in and don't affect your score
Timer auto-submits when time runs out
Your progress is auto-saved every 30 seconds