A baby of a mother with poorly controlled pregestational diabetes is born at 35 weeks gestation weighing appropriate for dates. Within 4 hours she develops grunting, retractions, and an oxygen requirement. Surfactant deficiency is confirmed. Why did this infant develop respiratory distress syndrome despite a gestational age at which the lungs are usually mature?
- A Maternal hyperglycaemia causes polyhydramnios and premature rupture of membranes
- B Diabetes accelerates pulmonary vascular remodelling causing persistent hypertension
- C Fetal hyperinsulinaemia antagonises the corticosteroid mediated induction of surfactant synthesis ✓
- D Maternal ketoacidosis suppresses fetal type II pneumocyte proliferation
Correct answer: C. Fetal hyperinsulinaemia antagonises the corticosteroid mediated induction of surfactant synthesis
Explanation
Insulin acts as a counter regulatory antagonist to cortisol, blunting the hormonal induction of phosphatidylcholine synthesis and lamellar body maturation in type II pneumocytes. Infants of diabetic mothers therefore remain at risk of respiratory distress syndrome even near term, and their lecithin to sphingomyelin ratio matures later than expected. This delayed maturation is the reason antenatal steroid cover and readiness for surfactant are emphasised in these deliveries.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.