A CASE-CONTROL STUDY OF UNEXPLAINED ANTEPARTUM STILLBIRTHS

Objective To ascertain factors that will identify women who are at increased risk of unexplained antepartum stillbirth. Design Matched case-control study. The cases and controls were initially analysed as a whole group and again after dichotomizing into those of low birthweight (<2500 g) and those of normal birthweight (greater-than-or-equal-to 2500 g). Setting Western Australia 1980-1983. Subjects Unexplained antepartum stillbirths of greater-than-or-equal-to 1000 g birthweight (cases) and liveborn infants individually matched for year of birth, plurality, sex and birthweight of infant and race of mother (controls). Results The case pregnancies had more polyhydramnios (OR 10.83, 95% CI 2.41-48.69) and cord problems (OR 6.57 95% CI 1.36-31.75) than the controls but, paradoxically, other obstetric and medical complications were less common in the cases. The association with polyhydramnios persisted when the analysis was confined to those with low birthweight. With normal birthweight fetal distress was more frequent in the cases (OR 3.65 95% CI 1.36-9.80) but there were few other differences. Conclusions The clinical and diagnostic systems currently in use are unable to identify many fetuses at risk of death. Decreases in the rate of unexplained antepartum stillbirths await the discovery of new preventable causes, or of innovations in clinical or laboratory aspects of obstetric care.