Stillbirth Risk in a Second Pregnancy

There are relatively few data on the recurrence rates of stillbirth, and available studies report a wide variation in risk. Factors known to be associated with stillbirth in a previous pregnancy may be predictive of the likelihood of stillbirth in a second pregnancy. Such factors include preterm birth, growth restriction, and cesarean delivery. The aim of this population-based cohort study was to estimate the risk of a subsequent stillbirth among pregnant women whose previous stillbirth was associated with risk factors such as preterm birth and small for gestational age (SGA). The study was conducted between 2002 and 2006 in Australia. Data from the New South Wales Midwives Data Collection and the New South Wales Perinatal Death Database were used to link singleton births in a first pregnancy to a second pregnancy. Perinatal deaths were classified according to the Perinatal Society of Australia and New Zealand Perinatal Death Classification System. Cox proportional hazards models were used to estimate crude hazard ratios and to adjust for potential confounders. There was a significant association between delivery of an SGA newborn in the first pregnancy and increased risk of stillbirth in a second pregnancy [adjusted hazard ratio (aHR),1.73; 95% confidence interval (CI), 1.15–2.60], with further increased risk if the SGA neonate was also premature (aHR, 5.65; 95% CI, 1.76–18.12). Stillbirth in the first pregnancy did not significantly increase the risk for stillbirth in the second pregnancy; aHR was 2.03, with a 95% CI of 0.60 to 6.90. The estimated absolute risk of stillbirth up to 40 completed weeks of gestation among women aged 30 to 34 years was 4.84 per 1000 among women whose first pregnancy was a stillbirth and 7.19 per 1000 among those whose first pregnancy was both preterm and SGA. These findings indicate that delivery of an SGA and preterm neonate in a first pregnancy increases the risk of stillbirth in a second pregnancy. However, in the absence of growth restriction and preterm birth, women with a prior stillbirth are generally at low risk of recurrence.