A baby born at 37 weeks to a mother with poorly controlled gestational diabetes develops jitteriness and a capillary glucose of 28 mg/dL two hours after birth. What is the mechanism of this hypoglycaemia?

• A Transplacental passage of maternal insulin
• B Delayed hepatic glucokinase maturation
• C Pancreatic hypoplasia from chronic intrauterine hypoinsulinaemia
• D Persistent fetal hyperinsulinism after abrupt withdrawal of maternal glucose supply ✓

Explanation

Chronic maternal hyperglycaemia exposes the fetus to excess glucose, driving fetal pancreatic beta cell hyperplasia and sustained hyperinsulinaemia. After cord clamping, the maternal glucose supply stops abruptly while insulin secretion remains high, causing neonatal hypoglycaemia within hours. Maternal insulin does not cross the placenta, which eliminates option A. Pancreatic hypoplasia would produce hyperglycaemia, not hypoglycaemia. The same hyperinsulinaemic mechanism explains neonatal polycythaemia, hypocalcaemia and respiratory distress syndrome.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.