Aboriginal and white births in Western Australia, 1980-1986. Part I: Birthweight and gestational age.

This article describes the distributions of birthweight and gestational age of all singleton Aboriginal and white live-born infants in Western Australia for the period 1980-1986. At early gestational ages, the mean birthweight was greater for Aboriginal infants. However, after 34-weeks' gestation for male infants and 32-weeks' gestation for female infants, the pattern was reversed. More Aboriginal infants were of low birthweight--male Aboriginal infants, 9.8%; male white infants, 4.0%; female Aboriginal infants, 12.4%; and female white infants, 4.6%, this excess only occurred in term (37- to 41-weeks' gestation) and post-term (42- to 52-weeks' gestation) infants. The birthweight distributions for Aboriginal and white infants were similar in preterm infants, but at term and beyond Aboriginal infants tended to be lighter. Preterm (fewer than 37-weeks' gestation) births were more common among Aborigines (male Aboriginal infants, 16.0%; white male infants, 6.8%; female Aboriginal infants, 15.9%; and female white infants, 6.0%). Thus, it seems that the distributions of both birthweight and gestational age in Aboriginal infants are shifted downward compared with those for white infants. Aboriginal infants normally may be smaller and more likely to be born earlier than are white infants as well as having a definite shift towards pathological growth retardation at term and beyond.