The effect of prepregnancy body mass index on the risk of gestational diabetes mellitus: A systematic review and dose‐response meta‐analysis

: This study was conducted to investigate the effect of the prepregnancy BMI on the risk of gestational diabetes mellitus (GDM). Five electronic databases, including PubMed, Scopus, Embase, Web of Science, and Google Scholar, were searched for literature published until 1 January 2018. The two-stage, random effect meta-analysis was performed to compare the dose-response relationship between BMI and GDM. As well as studies with categorized BMI, studies that treat BMI as a continuous variable were analysed. A total of 33 observational studies with an overall sample size of 962 966 women and 42 211 patients with GDM were included in analysis. The pooled estimate of GDM risk in the underweight, overweight, and obese pregnant women was 0.68, 2.01, and 3.98 using the adjusted OR and 0.34, 1.52, and 2.24 using the adjusted RR. The GDM risk increased 4% per unit of increase in BMI with both the crude and adjusted OR/RR models. Also, the risk of GDM increased 19% with the crude model and 14% with the adjusted model. The existence of dose-response relationship between the pre-pregnancy BMI and GDM can strengthen the scientific background for vigorous public health interventions for the control of pre-pregnancy BMI as well as the weight gain during pregnancy.