Risk factors and outcomes of fetal macrosomia in a tertiary centre in Tanzania: a case-control study

BACKGROUND Fetal macrosomia is defined as birth weight ≥4000 g. Several risk factors have been shown to be associated with fetal macrosomia. There has been an increased incidence of macrosomic babies delivered and the antecedent complications. This study assessed the risk factors, maternal and neonatal complications of fetal macrosomia in comparison with normal birth weight neonates. METHODS A case-control study was conducted at the Muhimbili National Hospital (MNH) maternity and neonatal wards. Cases comprised of neonates with birth weight ≥4000 g; controls were matched for sex and included neonates weighing 2500-3999 g. Detailed clinical and demographic information and laboratory investigations which included blood glucose, hematocrit and plasma calcium were collected. The child was followed up to discharge/death. RESULTS The prevalence of macrosomic babies was 2.3 % (103 out of 4528 deliveries). Mean birth weight of macrosomic babies was 4.2 ± 0.31 kg whereas in the controls it was 3.2 ± 0.35 kg. Maternal weight ≥80 kg, maternal age ranging between 30 and 39 years, multiparity, presence of diabetes mellitus, and gestational age ≥40 years, previous history of fetal macrosomia and delivery weight ≥80 kg were significantly associated with fetal macrosomia. Macrosomic infants were more likely to have birth asphyxia, shoulder dystocia, hypoglycemia, respiratory distress and perinatal trauma and increased risk of death compared to controls. Maternal complications such as postpartum hemorrhage, second degree perineal tears and prolonged labor occurred more frequently in the macrosomia group compared to controls (p-value <0.05), while shoulder dystocia, uterine rupture and maternal death were recorded only among the cases and none occurred in the controls. CONCLUSION Fetal macrosomia was an important cause of maternal and neonatal morbidity at Muhimbili National Hospital. Presence of risk factors should alert the obstetrician to closely monitor these pregnancies and plan on appropriate mode of delivery. Macrosomic neonates should be routinely screened and appropriately managed for hypoglycemia.