The epidemiological characteristics of unexplained antepartum stillbirths.

All antepartum stillbirths weighing 1000 g or more born in Western Australia from 1980 to 1983 were categorised as 'unexplained' or 'explained' based on information from Perinatal Death Certificates. Using data from hospital and doctors' antenatal records a number of variables in each stillbirth category were compared by unconditional logistic regression. Significant differences were observed between the two groups in medical disorders and abnormalities of pregnancy, thus confirming our classification system. Compared with mothers of 'explained' antepartum stillbirths, mothers of unexplained antepartum stillbirths tended to have younger ages at delivery and had associated lower parity, more antenatal visits to the medical practitioner, fewer hospital admissions, a greater chance of having received care by a general practitioner than by a specialist obstetrician and were of more advanced gestation at the time of diagnosis. The results of this study indicate that the epidemiological characteristics of pregnancies resulting in unexplained antepartum stillbirths differ from those resulting in explained antepartum stillbirths. This suggests that unexplained antepartum stillbirths are not merely the result of inadequate obstetrical management but consist of a series of fetal disease states which are not currently amenable to detection.