Strengths and Limitations
A key strength of this review is that it is the first to provide a comprehensive summary of evidence on the association between birth size or premature birth and future GDM risk. This study followed the methodological recommendations presented in the Cochrane Handbook, MOOSE guidelines, and GRADE criteria 27-29. Moreover, this study included previously unpublished data and a large sample size.
Nevertheless, this study has some limitations. First, the included studies were old and may not represent the current clinical practice. The definition of GDM proposed by the IADPSG in 2010 has resulted in an increase in GDM prevalence 2, 3, 53. For example, the prevalence of GDM in the United States increased from 4.6% in 2006 to 8.2% in 2016 53. The median prevalence of GDM in the control groups of the included studies was 2.9%. However, empirical evidence suggests that relative effect measures are, on average, consistent across different settings; in the present study, we estimated absolute risk differences separately for low-, moderate-, and high-prevalence settings54. Second, 5 of 15 studies divided birth size and preterm birth categories into three or more comparative groups, which could not be combined into two comparison groups of interest. This lack of data required methodological adjustments, as described previously. Lastly, this review only assessed certainty in estimates of association between prognostic factors and an outcome. Future studies are required to determine whether these factors can help risk-stratify pregnant women and improve the clinical management of GDM.