PU Fetal Biometry and Growth Assessment 2 — Questions and Answers
Question 1: Which bone is measured to assess femur length (FL) in fetal biometry?
- The longest bone in the fetal thigh (Correct answer)
- The longest bone in the fetal lower leg
- The humerus of the upper arm
- 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 2: What does a head circumference to abdominal circumference (HC/AC) ratio greater than 1.0 after 36 weeks suggest?
- Asymmetric IUGR (Correct answer)
- Symmetric IUGR
- Macrosomia
- Normal growth
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 3: Serial ultrasound exams to monitor fetal growth are typically performed how far apart?
- Every 3–4 weeks (Correct answer)
- Every week
- Every 6–8 weeks
- Daily
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 4: What is macrosomia defined as in ultrasound practice?
- Estimated fetal weight above the 90th percentile (Correct answer)
- Estimated fetal weight above the 75th percentile
- Birth weight over 3,000 grams
- Femur length above normal limits
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 5: Which measurement is most affected by fetal head shape variations such as dolichocephaly?
- Biparietal diameter (BPD) (Correct answer)
- Head circumference (HC)
- Abdominal circumference (AC)
- Femur length (FL)
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 6: The cephalic index (CI) is calculated as which ratio?
- BPD divided by occipitofrontal diameter × 100 (Correct answer)
- HC divided by BPD × 100
- AC divided by HC × 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.
PU Fetal Biometry and Growth Assessment 2
Which bone is measured to assess femur length (FL) in fetal biometry?