Epidemic of large babies highlighted by use of INTERGROWTH21st international standard

Objective: To compare birth weights in central Sydney to the INTERGROWTH21st international standard to describe current trends in relation to optimal growth and to define areas that may benefit from improved obstetric surveillance and intervention. Methods: Retrospective analysis of prospectively collected cohort. Design: hospital-based cohort study. Setting: Sydney Local Health District, Australia. Population or sample: women with singleton pregnancies who had first trimester screening for aneuploidy between 16 April, 2010 and 9 March, 2012. Analysis of 2966 births. Main outcome measures: Large for gestational age (LGA) >4000 g, >4500 g, >5000 g, >90th, >95th, >97th centiles and small for gestational age (SGA) <1500 g, <2500 g, <third, <fifth, <10th centiles. Results: The proportion of infants classified as LGA was significantly higher than expected by the international standard, with relative risks (RRs) of 1.66 (1.44–1.88), 1.81 (1.50–2.21) and 2.07 (1.61–2.65) for the 90th, 95th and 97th centiles, respectively (P < 0.0001). The number of infants classified as SGA was significantly lower with RRs of 0.32 (0.21–0.49), 0.38 (0.28–0.52) and 0.45 (0.37–0.55) for the 3rd, 5th and 10th centiles, respectively (P < 0.0001). Maternal body mass index (BMI) and height were significantly associated with LGA infants as were parity and pre-existing diabetes. Conclusion: Comparing the international INTERGROWTH21st standards to our population has revealed a markedly high prevalence of LGA infants. The most important modifiable risk factors identified in early pregnancy were maternal BMI and pre-existing diabetes.