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

Question 1: Which vessel is sampled in the ductus venosus Doppler assessment?

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

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

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

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

Fetal breathing movements
Gross fetal body movements
Placental weight (Correct answer)
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 4: What is the earliest structure visualized on transvaginal ultrasound in a normal intrauterine pregnancy?

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

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 5: Why is the maternal uterus assessed during pregnancy ultrasounds?

To detect maternal infections
To evaluate pelvic bone structure
To monitor fetal development and placental health (Correct answer)
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 6: What color Doppler setting adjustment is most important for detecting low-velocity venous flow?

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

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

Middle cerebral artery peak systolic velocity (MCA-PSV) >1.5 MoM in the anemic twin (Correct answer)
Reversed a-wave in the ductus venosus of the polycythemic twin
Elevated umbilical vein pulsatility index
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 8: What does an elevated pulsatility index (PI) in the uterine artery suggest in early pregnancy?

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

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

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

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

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

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

50-100 MHz
2-12 MHz (Correct answer)
1-5 MHz
15-30 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 12: Which type of placenta previa has the highest risk for cesarean delivery?

Complete placenta previa (Correct answer)
Low-lying placenta
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 13: Acardiac twinning (twin reversed arterial perfusion — TRAP sequence) occurs exclusively in which type of twin pregnancy?

Dichorionic-diamniotic twins only
Monochorionic-monoamniotic twins only
Monochorionic-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 14: At what gestational age does the placenta normally migrate away from the cervical os?

By 28–32 weeks as the lower uterine segment develops (Correct answer)
After 36 weeks
At 20 weeks
At 16 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 15: At what beta-hCG level should a gestational sac be visible on transvaginal ultrasound?

1,500–2,000 mIU/mL (Correct answer)
5,000 mIU/mL
10,000 mIU/mL
500 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 16: What is the primary purpose of 3D/4D ultrasounds in advanced pregnancy imaging?

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

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

8–10 weeks
18–22 weeks (Correct answer)
28–32 weeks
12–14 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 18: Nuchal fold thickness greater than how many millimeters at 16–20 weeks is considered abnormal?

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

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 19: What is the primary purpose of ultrasound in pregnancy?

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

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

20–28 weeks
6–12 weeks (Correct answer)
After 28 weeks
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 21: 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 22: What is vasa previa?

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

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

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

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

Infection
Neural tube defect
Aqueductal stenosis (Correct answer)
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 25: The 'stuck twin' appearance on ultrasound in TTTS refers to which specific finding?

One twin fixed in a persistent transverse lie
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

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 26: What is the banana sign in fetal ultrasound?

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

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

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

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 28: What is polyhydramnios defined as using the AFI?

AFI greater than 18 cm
AFI greater than 24 cm (Correct answer)
AFI greater than 20 cm
AFI greater than 30 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 29: Twin-to-twin transfusion syndrome (TTTS) occurs exclusively in which type of twin pregnancy?

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

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 30: 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)
1 layer (fused amnion)
2 layers (one amnion from each twin)
4 layers (two amnions and two chorions) (Correct answer)

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

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

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

Absent end-diastolic flow in the donor's umbilical artery
Hydrops in the recipient twin
Oligohydramnios in donor and polyhydramnios in recipient with a still-visible donor bladder (Correct answer)
Fetal demise of one 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 33: What does absent end-diastolic flow (AEDF) in the umbilical artery indicate?

Normal placental function
Mild IUGR only
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 34: 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 35: What does an increased nuchal translucency (NT ≥3.5 mm) indicate?

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

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 36: Which ultrasound finding is associated with placenta accreta spectrum?

Thick placenta over 5 cm
Bilobed placenta
Placenta in the fundus
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 37: When measuring nuchal translucency (NT) in a twin pregnancy, how should the measurement be performed?

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

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

Normal growth
Asymmetric IUGR (Correct answer)
Symmetric IUGR
Macrosomia

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

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

Question 40: Which fetal measurement best reflects fetal nutrition and soft tissue mass?

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

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

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

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

Routine imaging for every pregnancy
To monitor maternal hormone levels
When ultrasound findings are inconclusive, particularly for fetal brain or spine abnormalities (Correct answer)
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 43: The nuchal translucency (NT) measurement is performed at what gestational age range?

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

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 44: 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 45: What crown-rump length (CRL) corresponds to the first detectable fetal cardiac activity?

1 mm
2–4 mm (approximately 5.5–6 weeks) (Correct answer)
8–10 mm
15 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 46: In a naturally conceived triplet pregnancy, what is the most common chorionicity-amnionicity configuration?

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

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

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

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

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

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

Transducer (Correct answer)
Monitor
Amplifier
Probe

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 50: 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 51: Which measurement technique is preferred when the umbilical cord obscures fluid pockets in AFI assessment?

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

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

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

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 53: 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 54: What condition is suggested when all fetal biometric measurements are proportionally small?

Asymmetric IUGR
Normal variant
Symmetric IUGR (Correct answer)
Macrosomia

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

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

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 56: What is a succenturiate lobe of the placenta?

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

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

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

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 58: 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 59: What is the significance of an abdominal circumference crossing two major percentile lines downward on a growth chart?

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

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

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

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

To assess fetal movement and organ development
To confirm pregnancy, estimate gestational age, and check for multiples (Correct answer)
To detect placental abnormalities
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 62: Which measurement is considered the most accurate indicator of gestational age in the second trimester?

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

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 63: Which condition is most commonly associated with polyhydramnios?

Fetal gastrointestinal obstruction (Correct answer)
Fetal renal agenesis
Placenta previa
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 64: What does reversed flow in the ductus venosus (DV) indicate?

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

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 65: What is the intradecidual sign on early pregnancy ultrasound?

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

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 66: Why is fetal echocardiography performed during pregnancy?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

BPD-based formula
HC-based formula (Correct answer)
FL-based formula
AC-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 74: Why is transvaginal ultrasound preferred over transabdominal ultrasound in early first-trimester assessment?

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

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

50–60 bpm
180–220 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 76: What is the significance of the Doppler function in ultrasound?

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

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 77: 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 radius of the forearm
The longest bone in the fetal thigh (Correct answer)

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

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

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

AC divided by HC × 100
BPD divided by occipitofrontal diameter × 100 (Correct answer)
HC divided by BPD × 100
FL 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 80: What structure should always be visualized within a gestational sac before a CRL is measurable?

Fetal pole
Umbilical cord
Amnion
Yolk sac (Correct answer)

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 81: 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 82: When is Doppler ultrasound considered safe to use in pregnancy?

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

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

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

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

Myometrium (Correct answer)
Perimetrium
Decidua
Endometrium

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

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

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

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

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

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

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

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

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

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

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

Omphalocele
Gastroschisis
Esophageal atresia
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 91: What is the significance of bilateral renal pyelectasis on a second-trimester scan?

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

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

Trisomy 21 (Down syndrome)
Turner syndrome
Trisomy 18 (Edwards syndrome) (Correct answer)
Trisomy 13 (Patau 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 93: What is the S/D ratio in umbilical artery Doppler?

The ratio of peak systolic to end-diastolic velocity (Correct answer)
The ratio of systolic to mean velocity
The ratio of diastolic to systolic velocity
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 94: What is the mean sac diameter (MSD)?

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

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

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

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 96: What does placental grading assess on ultrasound?

Placental weight
Placental blood flow
Placental thickness
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 97: What AFI value defines oligohydramnios?

Less than 8 cm
Less than 5 cm (Correct answer)
Less than 10 cm
Less than 15 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 significance of a large-for-dates gestational sac (MSD > 25 mm) with no visible embryo?

Twin pregnancy
Anembryonic pregnancy (blighted ovum) (Correct answer)
Hydatidiform mole
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 99: What does an echogenic intracardiac focus (EIF) represent on ultrasound?

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

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

Gamma rays
Light waves
Sound waves (Correct answer)
X-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 101: What defines Quintero Stage II in twin-to-twin transfusion syndrome (TTTS)?

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

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

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

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

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

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 104: What is placenta previa?

A placenta implanted in the uterine fundus
A placenta that covers or is adjacent to the internal cervical os (Correct answer)
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 105: A bilobed placenta differs from a succenturiate lobe in that:

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

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

Placenta accreta
Fetal anemia (Correct answer)
IUGR
Ventriculomegaly

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

Cystic fibrosis, Down syndrome, or cytomegalovirus infection (Correct answer)
Gastroschisis
Normal variant only
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 108: At what atrial width measurement is ventriculomegaly diagnosed?

Greater than 8 mm
Greater than 10 mm (Correct answer)
Greater than 12 mm
Greater than 15 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 109: What is the purpose of uterine artery Doppler screening at 20–24 weeks?

To diagnose placenta previa
To assess fetal position
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 110: Which ultrasound parameter is used to calculate the ponderal index as an indicator of fetal nutrition?

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

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

Normal MCA and UA flow
Increased MCA flow with decreased umbilical artery flow indicating redistribution to protect the brain (Correct answer)
Decreased MCA flow with normal UA flow
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 112: What is a subchorionic hemorrhage (SCH) on first-trimester ultrasound?

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

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

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

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

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

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

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

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

Continuous flow
High velocity flow
Pulsatile umbilical venous flow (Correct answer)
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 117: 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 twin gestational sac
A subchorionic hemorrhage
A cornual pregnancy 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 118: What is the normal range for amniotic fluid index (AFI) in a term pregnancy?

25–35 cm
2–6 cm
1–5 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 119: What is the appropriate protocol for measuring fetal heart rate during an obstetric ultrasound?

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

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

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

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 121: What does IUGR stand for in obstetric ultrasound?

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

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

Angle correction
End-diastolic velocity
Mean velocity in the denominator (Correct answer)
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 123: What is macrosomia defined as in ultrasound practice?

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

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

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

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 125: What is the role of the cervix during pregnancy?

It nourishes the fetus.
It facilitates the production of amniotic fluid.
It maintains pregnancy by remaining closed and shortens during labor. (Correct answer)
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 126: What is the recommended timing of the first ultrasound to optimally determine chorionicity in a newly diagnosed twin pregnancy?

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

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

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

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

Thick corpus callosum
Enlarged cerebellum
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 129: Which ultrasound finding is associated with congenital diaphragmatic hernia (CDH)?

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

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 130: What ultrasound finding is the hallmark of anencephaly?

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

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

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

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.

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

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180 min

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70%

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