Trends in birth size and macrosomia in Queensland, Australia, from 1988 to 2005

Abstract

The objectives of this study were to explore temporal changes in birth measures in Queensland, Australia, and examine whether secular trends are similar to those in other countries. This study used data from the Queensland Perinatal Data Collection, including singleton livebirths (n = 831 375) from 1988 to 2005. Recorded birthweight (BW, g), birth length (BL, cm), gestational age (weeks), maternal age, ethnic origin and calculated ponderal index (PI, kg/m(3)) were used. Temporal trends were assessed over the intervals 1988-2005 for BW and 2001-2005 for BW, BL and PI. Mean BW increased during the 17-year interval by approximately 1.9 g/year at a relatively low rate compared with reports from other countries. The proportion of high BW infants (> or = 4000 g) rose by 0.8% per year. Stratification by Indigenous status indicated that the increase in mean BW and prevalence of high BW was confined to non-Indigenous newborns only. The secular increase in BW was further modified by gestational age, and maternal age. The increase in BW was larger in term infants (4.2 g/year) than in preterm infants (1.8 g/year), and larger in infants of younger mothers than in those of older mothers (5.0 g/year vs. 3.1 g/year). There were no trends in mean BL and mean PI at birth from 2001 to 2005. In Queensland, mean BW increased moderately in the last 17 years, as did the proportion of high BW infants. The trend in rising BW remained after controlling for other perinatal characteristics. Birth measures per se and related trends differed by Indigenous status and warrant further investigation.