Stillbirth recurrence in a population of relatively low-risk mothers

Abstract

We sought to estimate the risk of stillbirth recurrence among relatively low-risk women, a group defined as maternal age <35 years; absence of congenital anomalies; gestational age range of 20-44 weeks inclusive; singleton births; and non-smokers. The Missouri maternally linked data containing births from 1978 to 1997 were used for the study. We identified the study group (low-risk gravidae who experienced a stillbirth in the first pregnancy) and a comparison group (low-risk gravidae who delivered a live birth in their first pregnancy) and compared the stillbirth risks in the second pregnancy between both groups. Analysis was based on 261 384 women with information on first and second pregnancies [1050 (0.5%) women with stillbirth]. Of the 947 cases of stillbirth in the second pregnancy, 20 cases occurred in women with a history of stillbirth (stillbirth rate 19.0 per 1000 births) and 927 in the comparison group (stillbirth rate 3.6 per 1000 births; P<0.001). The adjusted risk of stillbirth was almost six times higher in women with a prior stillbirth (hazard ratio [HR] 5.8, [95% CI 3.7, 9.0]). Analysis by stillbirth subtype in the second pregnancy showed that history of stillbirth conferred greater risk for subsequent early (fetal deaths between 20 and 28 weeks) (HR 10.3, [95% CI 6.1, 17.2]) than late stillbirths (fetal deaths at >or=29 weeks) (HR 2.5, [95% CI 1.0, 6.0]); and for intrapartum (HR 12.2, [95% CI 4.5, 33.3]) than antepartum (HR 4.2, [95% CI 2.3, 7.7]) stillbirths. Among relatively low-risk women, history of stillbirth was associated with increased recurrence, with substantial heterogeneity by timing of stillbirth.