Australian national birthweight percentiles by sex and gestational age, 1998-2007

Objective: To present updated national birthweight percentiles by gestational age for male and female singleton infants born in Australia. Design and setting: Cross-sectional population-based study of 2.53 million singleton live births in Australia between 1998 and 2007. Main outcome measures: Birthweight percentiles by gestational age and sex. Results: Between 1998 and 2007, women in Australia gave birth to 2 539 237 live singleton infants. Of these, 2 537 627 had a gestational age between 20 and 44 weeks, and sex and birthweight data were available. Birthweight percentiles are presented by sex and gestational age for a total of 2 528 641 births, after excluding 8986 infants with outlying birthweights. Since the publication of the previous Australian birthweight percentiles in 1999, median birthweight for term babies has increased between 0 and 25 g for boys and between 5 g and 45 g for girls. Conclusions: There has been only a small increase in birthweight percentiles for babies of both sexes and most gestational ages since 1991-1994. These national percentiles provide a current Australian reference for clinicians and researchers assessing weight at birth.