Maternal disease, medication and substance effects on the fetus — formative SAQs

SAQ 1 — Valproate in pregnancy: counselling and prevention (20 marks, ~15 minutes)

A 26-year-old woman with juvenile myoclonic epilepsy, well controlled on sodium valproate, is found to be 8 weeks pregnant. She has been on valproate for 10 years and is frightened. She asks whether she should stop the medication immediately. [9]

Questions

1. Explain the principles of teratogenesis that determine the type of fetal harm from valproate, and why the timing of this presentation (8 weeks) is significant. (5 marks) [1]
2. Describe the specific risks and the named syndrome associated with fetal valproate exposure, including structural and neurodevelopmental effects. (5 marks) [11]
3. Outline your immediate counselling and management of this woman, including what you would and would not do with her medication. (5 marks) [9]
4. Describe the preventive measures that should ideally have been in place before conception, and what surveillance is now required for the remainder of the pregnancy. (5 marks) [2] [9]

Model answer (must-hit)

1. Teratogenic harm is timing-dependent: the first two weeks post-conception follow an all-or-none rule; weeks 3 to 8 (organogenesis) are the critical window for major structural defects; from week 9 onward the fetal period targets growth and neurodevelopment. At 8 weeks she is at the tail end of organogenesis — most structural risk has been incurred but neurodevelopmental risk continues. Valproate disrupts neural tube closure and histone deacetylase signalling, producing both structural defects and later neurodevelopmental harm. [1]
2. Fetal valproate spectrum disorder carries a major malformation rate around 6 to 10 percent — neural tube defects, cardiac anomalies and characteristic facies. Neurodevelopmental effects include reduced IQ, elevated autism risk and attentional difficulties, which may not be evident until early childhood. The 2019 European consensus statement codified the diagnosis. [11]
3. Do NOT stop valproate abruptly — uncontrolled seizures carry their own fetal and maternal risk. Refer urgently to neurology and perinatal medicine to individualise the risk-benefit balance and consider switching to lamotrigine or levetiracetam where the epilepsy phenotype allows. Counsel honestly about risk without adding anxiety about exposure that has already occurred. Confirm high-dose folic acid. [9]
4. Pre-conception, the ideal is a planned switch from valproate to the safest effective antiepileptic, high-dose folic acid 5 mg daily started before conception, reliable contraception until stable, and seizure optimisation. Antenatal surveillance now requires a detailed fetal anatomy ultrasound at 18 to 20 weeks and a fetal echocardiogram, with planned developmental follow-up of the child. [2] [9]

SAQ 2 — Infant of a diabetic mother: neonatal hypoglycaemia and surveillance (20 marks, ~15 minutes)

A term infant, birth weight 4.3 kg, is born to a mother with pre-existing type 1 diabetes. Her HbA1c at conception was 78 mmol/mol. At 2 hours of age the infant is jittery, the bedside glucose is 1.6 mmol/L, and the infant has fed once with a variable latch. [5]

Questions

1. Explain why infants of diabetic mothers are at higher risk of neonatal hypoglycaemia and name the mechanism. (4 marks) [4]
2. Explain why periconception glycaemic control matters more than third-trimester control for congenital anomalies, and name the major fetal structural effects of poorly controlled maternal diabetes. (5 marks) [4] [5]
3. Outline your immediate management of this infant's hypoglycaemia, including feeding, glucose monitoring and escalation. (5 marks) [5]
4. Describe the longer-term surveillance this infant needs, including the neonatal examination focus and developmental follow-up. (6 marks) [4] [6]

Model answer (must-hit)

1. Maternal hyperglycaemia drives fetal hyperinsulinaemia via placental glucose transfer. After cord clamping the glucose supply is cut but the hyperinsulinaemia persists, producing reactive hypoglycaemia in the first hours of life. The infant of a diabetic mother is the prototypical at-risk group. [4]
2. Cardiac, neural tube, renal and skeletal organogenesis is complete by approximately 7 to 8 weeks post-conception, before many women know they are pregnant. A high periconception HbA1c predicts congenital anomalies; the major effects are cardiac (conotruncal and septal defects), neural tube defects, caudal regression and renal anomalies. Third-trimester control drives macrosomia and neonatal metabolic complications but not the structural anomalies. [4] [5]
3. Immediate management is early feeding, repeat glucose monitoring per local protocol, and if glucose remains below the operational threshold despite feeding, buccal 40 percent dextrose gel combined with a feed and recheck, then intravenous 10 percent dextrose if still below threshold. State that you would use the current local neonatal protocol rather than a memorised number. [5]
4. Targeted neonatal examination focuses on the cardiac system (murmur, femoral pulses, signs of heart failure), the sacral spine (caudal regression), renal system, and birth injury (brachial plexus, clavicle) related to macrosomia. Long-term developmental surveillance is needed because maternal diabetes is associated with elevated offspring risk of obesity, impaired glucose tolerance and neurodevelopmental differences. [4] [6]