Hypoglycemia is defined as blood glucose of less than 40 mg/dL, irrespective of the gestational age. Causes of hypoglycemia Let us see each option one by one. Option ‘a’ IUGR “Hypoglycemia is due to shortage of glycogen reserve in the liver as a result of chronic hypoxia” Dutta Obs. 6/e, p 465 Option ‘b’ Mother with hypothyroidism Maternal hypothyroidism can cause hypoglycemia if it leads to fetal hypothyroidism also but “Maternal TSH receptor bloking antibodies can cross the placenta and cause fetal thyroid dysfunction.They however have little or no effect on fetal thyroid function even though they too cross the placenta.”. Williams 23/e, p 1131, 1132 So according to latest editon of Williams, maternal hypothyroidism does not lead to fetal hypothyroidism, thus it does not cause fetal hypoglycemia. Option ‘c’ Rh incompatibility There is no definite correlation between Rhincompatibility and hypoglycemia. Option ‘d’ Macrosomia Macrosomia usually is due to maternal diabetes which inturn results in fetal hyperinsulinemia due to beta cell hyperplasia, which further results in neonatal hypoglycemia. Dutta Obs. 6/e, p 287 Option ‘e’ Hyperthyroidism : Hyperthyroidism is a diabetes like state with increased insulin resistance.