The analysis of factors predicting antepartum stillbirth.

Antepartum stillbirth is the single most common cause of perinatal death. Antepartum stillbirth is associated with fetal abnormality, congenital infection, rhesus isoimmunisation, maternal medical conditions, and complications of pregnancy, such as pre-eclampsia and placental abruption. However, the majority have no direct obstetric cause and are referred to as unexplained. Many of these so-called unexplained deaths are associated with growth restriction. Maternal characteristics, such as age and smoking, are associated with an increased risk of antepartum stillbirth. The risk of stillbirth in late pregnancy is related to the function of the placenta in early pregnancy. Placental function can be assessed using circulating markers in the mothers blood, such as pregnancy associated plasma protein A and alpha-fetoprotein. Invasion of the trophoblast into the uterine vessels is associated with decreased resistance to flow in the uterus and impaired placentation is reflected in high resistance Doppler flow velocity waveforms in the utero-placental circulation. Both circulating placental markers and Doppler indices of resistance to flow are predictive of the risk of antepartum stillbirth. However, none of these tools has sufficient positive predictive value to justify population based screening. Future research in unexplained stillbirth should be directed towards developing better predictive tests to identify women at high risk and the evaluation of interventions in large scale trials.