Birth size of Australian aboriginal babies.

OBJECTIVES: (i) To describe birth size of Aboriginal babies by sex, gestational age, and Aboriginality; (ii) to analyse the results with reference to standards of ponderal index and birthweight for gestational age.

SUBJECTS: 570 liveborn singletons routinely delivered at Royal Darwin Hospital between January 1987 and March 1991, and recorded in the Delivery Suite Register as being born to an Aboriginal mother.

MAIN OUTCOME MEASURES: Weight, length and head circumference at birth.

RESULTS: The mean birthweight was 3098 g (standard deviation, 601 g), peak gestational age was 39 weeks, 13% were low birthweight and 7% were preterm. Preterm rates did not differ significantly for sex and Aboriginality. Babies without a non-Aboriginal ancestor had a lower mean birthweight and at term, were significantly smaller than babies with a non-Aboriginal ancestor as assessed by mean birthweight, length, head circumference and ponderal index. More than a quarter of babies (27%) without a non-Aboriginal ancestor were below the 10th percentile of birthweight for gestational age, compared with 14.2% of babies with a non-Aboriginal ancestor.

CONCLUSIONS: On the basis of postnatal clinical estimates of gestational age, Aboriginal babies have a preterm rate of 7% and Aboriginal babies without a non-Aboriginal ancestor are smaller in size at birth than babies with a non-Aboriginal ancestor.