The effect of terminations of pregnancy for fetal abnormalities on trends in mortality to one year of age in Western Australia

Many studies documenting the decline in all-cause infant mortality rates over the past 20 years have highlighted the contribution of birth defects. Over this time there has also been an increasing number of terminations of pregnancy for fetal abnormality. However, the effect of these terminations on mortality rates in Australia has not yet been estimated. The Western Australian Birth Defects Registry (BDR) records all birth defects that are diagnosed in stillbirths, livebirths and in pregnancies terminated because of a fetal abnormality. All cases on the BDR over the period 1980-98 were categorised into one of eight main birth defect groups and analysed in four time periods to show trends. Linkage provided information on deaths to one year of age, defined as perinatal plus postneonatal deaths. The proportion of terminations for fetal abnormality that would have resulted in a death before one year of age was estimated in two ways. The first method used the proportion of births with a birth defect in each diagnostic category that resulted in a death. The second method involved determination of likelihood of survival to one year of all terminations for fetal abnormality through independent review by two experts. Whilst mortality to one year of age for all birth defects has declined from 4.36/1000 births in 1980-84 to 2.75/1000 births in 1995-98, terminations of pregnancies for fetal abnormalities increased from 1.19/1000 births to 4.70/1000 births. After including the estimated mortality associated with terminations for fetal abnormality, the decline in mortality to one year of age associated with birth defects from 1980 to 1998 changed from a 37% reduction to a 15% reduction based on observed mortality 1980-84, and an 11% increase in mortality based on individual case review, highlighting the importance of considering terminations in mortality analyses.