A 24-year-old pregnant lady in 2nd trimester comes to your clinic worried about her exposure to CXR done for suspicion of pneumonia last week; she is highly concerned about possibility of congenital anomalies. Of the following, the BEST advice to her is that

Correct Answer: D

Rationale: A single chest X-ray (low dose, <0.1 mGy) is negligible. Rationale: Fetal risk is significant only >50 mGy; 2nd trimester is less sensitive than 1st.

Correct Answer: A

Rationale: Patau syndrome (trisomy 13, A) matches microcephaly, polydactyly, and rocker-bottom feet. Rationale: Single nostril (holoprosencephaly) is classic Patau.

Correct Answer: B

Rationale: Tay-Sachs is an autosomal recessive disorder caused by a single genetic defect in the HEXA gene, leading to enzyme deficiency. While more common in Ashkenazi Jews, it’s not exclusive to them. It affects both sexes, lacks genetic heterogeneity in its classic form, and is infantile-onset, not adult.

Correct Answer: C

Rationale: Multifactorial inheritance involves multiple genes and environment, with sex predilection (e.g., pyloric stenosis), recurrence rates of 2-10%, and twin concordance of 20-63%. Severe symptoms can increase risk. Symptomatic carriers apply to monogenic traits, not multifactorial.

Correct Answer: D

Rationale: The ‘double bubble’ sign on KUB indicates duodenal atresia, common in Down syndrome, causing a gas bubble in the stomach and proximal duodenum. Hirschsprung, meconium ileus, and plugs cause distal obstructions. Pyloric atresia is rarer and doesn’t produce this sign.