A 28-year-old diabetic patient with pre-gestational Type 1 DM at 10 weeks has HbA1c 9.4%. She is on multiple daily injections. Which congenital anomaly is MOST specifically associated with poor periconceptional glycemic control at this HbA1c level?

• A Ventricular septal defect — the most common cardiac anomaly in diabetic pregnancies
• B Neural tube defects — the most common major structural anomaly seen with elevated HbA1c
• C Renal agenesis — maternal hyperglycemia causes mesenchymal apoptosis in renal anlage
• D Caudal regression syndrome (sacral agenesis) — highly specific to diabetic embryopathy ✓

Explanation

Caudal regression syndrome (sacral dysgenesis/agenesis) is the most pathognomonic congenital anomaly of diabetic embryopathy, with a 200-fold increase in risk compared to non-diabetic mothers. While it is rare in absolute terms, it is virtually diagnostic of maternal diabetes when present. Cardiac defects (TGA, VSD, heterotaxy) are the most common anomalies overall in diabetic pregnancies. NTDs are increased but not as specifically associated with diabetes. Diabetic embryopathy primarily affects structures developing during weeks 5–8 (organogenesis), when glycemic control is most critical.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.