Maternal Bereavement During Pregnancy and the Risk of Stillbirth

Abstract

Stillbirth is an extremely painful event that is associated with deep long-term grief and psychological morbidity. The etiologies of all stillbirths are not fully understood, although increasing evidence suggests that in some cases maternal psychosocial stress during pregnancy may impair fetal growth, which can lead to stillbirth. To date, no study has investigated the role of antenatal stress in the etiology of stillbirth. This population-based cohort study was performed to examine whether maternal bereavement during pregnancy is associated with an increased risk of stillbirth. The Swedish Medical Birth Register was used to identify all births (n = 3,413,812) occurring at 28 weeks’ gestation or greater from 1973 to 2006. The study cohort included 11,071 stillbirths (3.8/1000 births; 10,063 antenatal and 1008 intrapartal); 2101 (4.5/1000 births) stillbirths also occurred among excluded infants born at 28 weeks’ gestation or greater (n = 466,123). A fetus was considered to be prenatally exposed to maternal bereavement if the mother lost an older child, a sibling, or a parent in the year before or during pregnancy. Cox regression models were used to investigate the association between maternal bereavement during pregnancy and the risk of stillbirth. Exposure was treated as a time-dependent variable, with 5 exposure periods: 7 to 12 months before pregnancy, 0 to 6 months before pregnancy, and the first, second, and third trimesters. Causes of death were categorized as unexpected versus natural death. The exposed group was classified into infants whose mother was grieving an older child, a sibling, or a parent. In a population of 2,930,870 births, 86,372 (2.9%) fetuses were prenatally exposed to maternal bereavement of a close relative, although, unfortunately, the data set had no information on the death of spouses. The exposed and unexposed groups were comparable with respect to sex, proportion of multiple pregnancies, maternal prepregnancy diabetes or chronic hypertension, obesity, preeclampsia, and antepartum hemorrhage. In the adjusted analysis, infants of bereaved mothers had a higher risk of stillbirth than did unexposed offspring; the hazard ratio was 1.18 (95% confidence interval [CI], 1.06–1.31). Hazard ratios were 1.67 (95% CI, 1.18–2.36) for maternal loss of an older child, 2.06 (95% CI, 1.44–2.94) for loss of a sibling, and 1.07 (95% CI, 0.95–1.21) for loss of a parent. Exclusion of exposed infants whose older sibling died neonatally did not substantially change the association between bereavement of any relative and stillbirth, whereas the hazard ratio corresponding to the loss of a child became 1.40 (95% CI, 0.85–2.31). The relationship between maternal bereavement and stillbirth did not differ when outcomes were stratified as antepartum versus intrapartum stillbirth or as preterm versus term stillbirth. No strong evidence emerged on the effect measure modification by maternal age, education, country of birth, or infant sex of the association between maternal bereavement and stillbirth risk (all P values for interaction ≥0.05). Maternal bereavement during pregnancy was associated with an increased risk of stillbirth. The relationship was stronger for maternal loss of a sibling or an older child than for loss of a parent and generally did not differ by time of exposure or by whether the relative’s death was expected or unexpected. These results provide new information on a factor that can potentially be linked to stillbirth. Additional studies are necessary to determine whether less severe but common stressors are associated with stillbirth.