Correct Answer: B. Gestational diabetes
Gestational diabetes mellitus (GDM) is the most likely diagnosis in a mother with a preterm infant born at 34 weeks. The clinical presentation described—a baby born prematurely—is a hallmark complication of poorly controlled GDM. Maternal hyperglycemia leads to fetal hyperinsulinemia, causing macrosomia, polyhydramnios, and increased risk of preterm labor and delivery. In India, GDM prevalence is 16–20% in urban populations (ICMR-INDIAB study), making it a leading cause of adverse perinatal outcomes. The preterm delivery at 34 weeks, combined with maternal metabolic dysfunction, strongly suggests GDM rather than gestational hypertension (which causes growth restriction, not prematurity with the described phenotype). GDM-exposed infants often present with features of macrosomia despite prematurity, hypoglycemia, hypocalcemia, and polycythemia. The mother's glycemic control during pregnancy directly determines fetal outcomes; uncontrolled GDM increases preterm labor risk by 2–3 fold. This is the classic presentation taught in Indian obstetric curricula and aligns with FOGSI guidelines on GDM screening and management.
Why the other options are wrong
A. Gestational hypertension — Gestational hypertension causes intrauterine growth restriction (IUGR) and small-for-gestational-age (SGA) infants, not the macrosomic or metabolically compromised phenotype seen here. While it can cause preterm delivery, it does so through placental insufficiency and maternal complications (preeclampsia), not through fetal hyperinsulinemia. The clinical picture of a 34-week infant with metabolic derangements is inconsistent with hypertensive disorders. C. Hypothyroidism — Maternal hypothyroidism increases miscarriage and stillbirth risk, but does not typically cause preterm delivery at 34 weeks as the primary manifestation. Congenital hypothyroidism in the infant (cretinism) presents with delayed milestones, coarse features, and developmental delay—not acute metabolic derangement at birth. Hypothyroidism is not a recognized cause of the acute neonatal metabolic complications associated with GDM. D. Rubella — Congenital rubella syndrome (CRS) causes intrauterine growth restriction, cardiac defects (PDA, pulmonary stenosis), cataracts, deafness, and microcephaly—a constellation of structural anomalies. It does not cause the metabolic derangements (hypoglycemia, hypocalcemia, polycythemia) or macrosomia typical of GDM. CRS is now rare in India due to vaccination programs; the clinical picture described does not match CRS phenotype.
High-Yield Facts
- Preterm delivery is a major complication of GDM, occurring in 15–25% of pregnancies; maternal hyperglycemia triggers preterm labor via polyhydramnios and uterine overdistension.
- Macrosomia despite prematurity is pathognomonic for GDM; fetal hyperinsulinemia drives adipose tissue deposition even at 34 weeks.
- Neonatal hypoglycemia occurs in 5–15% of GDM-exposed infants within 1–2 hours of birth due to persistent fetal hyperinsulinemia after cord clamping.
- Indian GDM prevalence is 16–20% in urban populations; FOGSI recommends universal screening at 24–28 weeks using 75 g OGTT.
- Gestational hypertension causes SGA/IUGR, not macrosomia; preterm delivery in hypertensive disorders is secondary to maternal complications, not fetal metabolic dysfunction.
Mnemonics
GDM vs Hypertension in Preterm Delivery GDM = BIG baby + Preterm (macrosomia, metabolic chaos). Hypertension = SMALL baby + Preterm (IUGR, placental insufficiency). Use this to discriminate: if the preterm infant appears large or metabolically deranged, think GDM; if small and growth-restricted, think hypertension. Neonatal Complications of GDM (CHOPS) Cardiac (cardiomyopathy), Hypoglycemia, Obesity/macrosomia, Polycythemia, Shoulder dystocia. These acute metabolic and structural complications distinguish GDM from other maternal conditions.
NBE Trap
NBE pairs preterm delivery with gestational hypertension because both cause prematurity; the trap is forgetting that hypertension causes SGA/IUGR, whereas GDM causes macrosomia and metabolic derangement. The clinical phenotype of the infant (not just the timing of delivery) is the discriminator.
Clinical Pearl
In Indian obstetric practice, a preterm infant born to a mother with poor glycemic control often presents with "fat baby syndrome"—macrosomia despite prematurity, hypoglycemia within minutes of birth, and polycythemia. Bedside capillary glucose testing and early feeding are critical; this phenotype is virtually pathognomonic for GDM and warrants immediate maternal glucose screening if not already done.
_Reference: DC Dutta's Textbook of Obstetrics, Ch. 24 (Diabetes in Pregnancy); FOGSI Guidelines on GDM (2018)_