Obstetric outcome of excessively overgrown fetuses (> or = 5000 g): a case-control study

To compare the obstetric outcome of excessively- and appropriately-grown fetuses.

Medical records of mothers who delivered excessively overgrown fetuses, defined as birthweight > or = 5000 g, in our hospital between 1996 and 2000 (n = 47, study group), and a control group who delivered fetuses with normal birthweight (n = 47) were reviewed.

Incidence of excessively overgrown fetuses was 0.24% and 68% were boys. Mothers in this group were significantly older, overweight and multiparous (p < 0.0001) and had gestational diabetes mellitus (p < 0.0001) and prolonged pregnancies (p = 0.04). A previous big baby was also significant (p < 0.0001) and the commonest risk factor. There were no obvious risk factors in nine (19.1%) cases. More than half (n = 28, 59.5%) of these babies were delivered vaginally without clinical suspicion of excessive fetal size. Duration of second stage of labor and incidence of maternal trauma were similar in both groups. Cesarean delivery (p = 0.0003), postpartum hemorrhage (p = 0.004), birth asphyxia (p = 0.007), shoulder dystocia (p < 0.0001) and fetal trauma (p = 0.03) were significantly more frequent in the study group.

Excessively overgrown fetuses are associated with the same risk factors as fetal macrosomia and should be delivered by cesarean if diagnosed antenatally because of increased maternal and perinatal morbidity during vaginal delivery.