Why do Aboriginal newborns weigh less? Determinants of birthweight for gestation

Objective: To compare birthweight for gestational age of Aboriginal with Caucasian infants and investigate the origins of their differences. Methodology: Data pertaining to birthweight, gestational age at delivery and pathological factors were abstracted from birth records of 1301 Western Australian singleton Aboriginal pregnancies dated before 24 weeks by ultrasound fetometry and compared with routinely collected data pertaining to Caucasian births of the same period. Results: Median birthweight for gestation was lower in Aboriginal than in Caucasian infants for deliveries after 35 weeks of gestation, and that of pure-descent lower than that of mixed-descent Aboriginal infants at all gestations. Pathological factors (e.g. diabetes, urogenital infections, alcoholism and leprosy) occurring more commonly in Aboriginal than in Caucasian pregnancies accounted for most of the differences in birthweight for gestation between mixed-descent Aboriginal and Caucasian infants but a discrepancy of almost 180 g remained between pure-descent Aboriginal and Caucasian infants. Conclusions: Identified pathological factors contribute but do not entirely explain the lower birthweights for gestation observed in Aboriginal infants.