Risk factors for antepartum and intrapartum stillbirth.

Data from married women who participated in the 1980 National Natality Survey and the National Fetal Mortality Survey were used for a case-control study of antepartum and intrapartum stillbirth. Risk factors were identified by comparing antepartum deaths and intrapartum deaths to livebirths in separate logistic regression analyses. Risk of antepartum death was increased among black mothers, those having their first delivery, those aged 35 years or more, and those with less education. Smoking cigarettes was associated with increased risk. For intrapartum deaths, total abstention from alcohol during pregnancy was associated with increased risk in the best-fitting logistic model, as was first delivery. Body mass index was logit-linear in both models, with lower body mass index associated with lower risk. While some of these factors have already been associated with stillbirth, others have not; the new associations may reflect the continuum of loss over the gestational period, bias in the study, or clues to mechanisms by which the risk of death, before or during parturition, is increased.