Gestational-age-specific stillbirth risk among Australian Aborigines.

Background: Previous studies have found that, for preterm babies, the risk of stillbirth among Australian Aborigines is similar to the risk for whites. In contrast, at full term, the risk for Aborigines is more than twice the risk for whites. However, these studies (like most other analyses of stillbirths) used the number of births at each gestational age to calculate the risk. For stillbirths, the risk is more appropriately estimated using the number of babies in utero. This paper presents the first comparison of stillbirth risk for Australian Aborigines and whites using the more appropriate denominator.

Methods: I used 6 years of data (1987-1992) from the routinely-maintained Queensland Perinatal Data Collection. Contingency-table analyses were used to compare the gestational-age-specific risk of stillbirth in Aborigines and whites. Multiple births were excluded; male and female babies were analysed separately.

Results: When the number of babies in utero was used as the denominator, preterm Aborigines had a statistically significant three- to fourfold increase in the risk of stillbirth compared with whites. At full term, the risks for Aborigines and whites were not statistically significantly different.

Conclusions: A different pattern of gestational-age-specific stillbirth risk was obtained when the appropriate denominator was used. Specifically, the high risk of stillbirth for preterm Aborigines was revealed. Research is needed to identify the causes of the Aboriginal-white difference in stillbirth risk for preterm babies.