Differing influences on Aboriginal and non-Aboriginal neonatal phenotypes: a prospective study

Objective: To understand the differences, if any, in major influences on birth phenotype between Aboriginal and non-Aboriginal neonates. Design: Prospective study of a cohort of pregnant Aboriginal women presenting for antenatal care before 20 weeks' gestation (ultrasound proven), and a reference cohort of pregnant non-Aboriginal women. Comparison of the phenotypic and demographic characteristics of the women, their pregnancies and their babies. Participants: 96 Aboriginal and 96 non-Aboriginal women with no known medical factors affecting fetal growth or gestation. Setting: Four remote far north Queensland communities served by the Far North Regional Obstetric and Gynaecological Service (FROGS) and the antenatal clinic at Cairns Base Hospital. Main outcome measures: Neonatal birth weight, length, head circumference, abdominal circumference, mid-arm circumference and triceps skinfold thickness, and derived ponderal index (weight/length(3)), head:abdomen circumference ratio and head:mid-arm circumference ratio. Results: The Aboriginal neonates were on average almost 450 g lighter than their non-Aboriginal counterparts. They were also slightly shorter, with smaller head, abdomen and mid-arm circumferences and lower mean ponderal indices and triceps skinfold thickness. The gestational characteristics of the two groups were not significantly different. Neonatal phenotype was significantly associated with maternal body mass index and maternal age in both groups. Alcohol use in pregnancy was associated with a significant reduction in Aboriginal neonatal size, while tobacco use was significantly associated with size reductions in non-Aboriginal babies. Conclusions: Culturally appropriate antenatal care programs targeting the effects of poor nutrition and excessive alcohol use are needed if the excess incidence of low birthweight in Aboriginal people is to be reduced.