Abstract / Summary
There is conflicting evidence on the impact of the recent increase in GDM rates on adverse neonatal outcomes. This study aimed to describe temporal trends in rates of adverse neonatal outcomes among pregnancies with and without GDM and compare risk of these outcomes for GDM by delivery periods. We performed a population-based retrospective cohort study using data from Ontario provincial birth registry linked with health administrative databases. All hospital deliveries with a singleton live birth or stillbirth from April 2012 to March 2020 in Ontario, Canada were included. We used modified robust Poisson regression to assess the risks of adverse neonatal outcomes associated with GDM using risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI) by delivery periods. Among 1 044 258 pregnant individuals, there were 82 896 (7.9%) with GDM and 172 442 (16.5%) with one or more diagnoses of severe neonatal morbidity and mortality. The annual rate of GDM increased from 6.1 to 10.5 per 100 deliveries between 2012/13 and 2019/20. Although the rate of severe neonatal morbidity and mortality (SNM) increased over time among pregnancies with and without GDM, the positive association between GDM and SNM was stable between the time periods (adjusted RR [95% CI], 2012/13-2015/16: 1.50 [1.48, 1.52] and 2016/17-2019/20: 1.54 [1.52, 1.56]). The strength of the association between GDM and both LGA and macrosomia decreased in 2016/17-2019/20 (2012/13-2015/16: 1.42 [1.39, 1.45] and 2016/17-2019/20: 1.31 [1.28, 1.34] for LGA; 2012/13-2015/16: 0.98 [0.95, 1.02] and 2016/17-2019/20: 0.86 [0.83, 0.90] for macrosomia). The associations of GDM with other neonatal outcomes remained similar over time. Our large, population-based study showed that, despite the recent increase in GDM, in Ontario, Canada, the relative risk of overall SNM for GDM remained stable over time. Except for the attenuated association of GDM with LGA and macrosomia, no significant changes were observed in associations of GDM with other individual neonatal outcomes. Future large studies are warranted to better understand the long-term impact of the increasing rate of GDM on adverse neonatal outcomes.