A 4.2 kg baby born to diabetic mother develops seizures at 16 hours. The most likely cause is:

Gestational diabetes mellitus (GDM) is associated with an increased risk of maternal and fetal complications including preeclampsia, stillbih, and macrosomia. Infants born to mothers with gestational diabetes are at increased risk of hypoglycemia, hyperbilirubinemia, hypocalcemia, and RDS. The signs of hypoglycemia in the newborn infant may be nonspecific and subtle: lethargy, poor feeding, irritability, tremors, jitteriness, apnea, and seizures. Hypoglycemia in hyperinsulinemic states can develop within the first 30-60 minutes of life. Ref: Thilo E.H., Rosenberg A.A. (2012). Chapter 2. The Newborn Infant. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.