Association between maternal diabetes mellitus and the risk of congenital malformations: A meta-analysis of cohort studies.

Increasing studies suggest that gestational diabetes mellitus (GDM) and pre-gestational diabetes mellitus (PGDM) may be associated with an increased risk of major congenital malformations (MCM) in the offspring. To determine whether GDM or PGDM is associated with an increased risk of congenital malformations, we performed a meta-analysis of cohort studies. We systematically searched the PubMed, Web of Science and Cochrane Library (from January, 1990 to October, 2014) and reviewed the reference lists of included papers to search for additional studies. Meta-analysis tools were used to summarize results. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated with random-effects models or fixed-effects models. Study quality was assessed using the Newcastle-Ottawa scale. A total of 21 cohort studies were included in the meta-analysis. Analysis of all studies showed that both PGDM and GDM were associated with an increased risk of MCM (RR=2.44, 95% CI=1.92-3.10, I2=78.3%, p=0.342; RR=1.11, 95% CI=1.11-1.27, I2=9.9%, p<0.001, respectively). There is a slightly higher risk of major congenital malformations in women with GDM than in the reference group. However, this risk is much lower than in women with PGDM. Further large-scale prospective cohort studies are needed to test the effect of PGDM and GDM on specific congenital malformations risk.