Aims: To identify factors, including the loss of a previous pregnancy before 20 weeks gestation, which are associated with increased risk of singleton antepartum unexplained fetal death (UFD) in Western Australia (WA) using information recorded in routine data collections.
Methods: All fetal deaths in WA from 1990 to 1999 that underwent thorough post-mortem investigations were classified using the Perinatal Society of Australia and New Zealand Perinatal Death Classification System. All UFDs were selected as cases and unmatched controls were randomly drawn from all live births in WA occurring during the study period. Demographic and clinical information on cases and controls was obtained from the WA Midwives' Notification System. Multivariable logistic regression was carried out to determine the independent effect of risk factors and calculate odds ratios.
Results: Almost one quarter (22%) of stillbirths were unexplained. Primigravid and primiparous women with a history of pregnancy loss before 20 weeks were at higher risk of UFD than multiparous women who had not experienced any loss. Women with a history of fetal death (after 20 weeks) had the highest risk of UFD.
Conclusion: The current practice of closely monitoring pregnant women with a history of fetal loss or death should continue as this study suggests they may have a higher risk of poor obstetric outcome. Larger studies are needed to confirm the association between previous pregnancy loss and UFD.