Wisconsin Stillbirth Service Program: analysis of large for gestational age cases

Since its inception in 1983, the Wisconsin Stillbirth Service Program (WiSSP) has reviewed over 2,600 referrals. Among 2,451 with fetal weight and gestational age recorded, 186 (7.6%) were large for gestational age (LGA), which is more than expected. We reviewed these cases to identify factors causing or contributing to fetal death as well as increased fetal size. LGA losses tended to occur later in pregnancy than non-LGA losses. The most common cause of death in LGA fetuses was fetal (43.5%), followed by placental (22.6%), and maternal (11.2%), which contrasts with previous studies involving the same database, but unselected for fetal weight, in which 21.5%, 40.0%, and 12.7% had fetal, placental, and maternal causes, respectively. The most common fetal cause was hydrops (60 cases/32.4%), which was most frequently idiopathic (16/26.6%), followed by cardiac (11/18.3%), Turner syndrome (8/13.3%), and twin-twin transfusions (6/10.0%). Placental causes, most commonly abruption and infarct, were more frequent in diabetic mothers, accounting for 33% versus only 18% in the entire LGA group. In the LGA group overall, 21% of mothers were diabetic, and most stillbirths in diabetic mothers occurred after 28 weeks. Despite large placentas (>95th centile) in 71.8% of the LGA cohort compared to 11% previously reported in the entire database, the most extreme LGA cases had a high fetoplacental ratio. We recommend pathologic evaluation of placentas from all stillbirths, close follow-up of pregnancies complicated by diabetes, and continued research into causes and pathophysiology of hydrops.