Risk of pre-eclampsia in women taking metformin: a systematic review and meta-analysis

Publication Type:
Journal Article
Diabetic Medicine, 2018, 35 (2), pp. 160 - 172
Issue Date:
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© 2017 Diabetes UK Aims: To perform meta-analyses of studies evaluating the risk of pre-eclampsia in high-risk insulin-resistant women taking metformin prior to, or during pregnancy. Methods: A search was conducted of the Medline, EMBASE, Web of Science and Scopus databases. Both randomized controlled trials and prospective observational cohort studies of metformin treatment vs. placebo/control or insulin either prior to or during pregnancy were selected. The main outcome measure was the incidence of pre-eclampsia in each treatment group. Results: Overall, in five randomized controlled trials comparing metformin treatment (n = 611) with placebo/control (n = 609), no difference in the risk of pre-eclampsia was found [combined/pooled risk ratio (RR), 0.86 (95% CI 0.33–2.26); P = 0.76; I 2  = 66%]. Meta-analysis of four cohort studies again showed no significant effect [RR, 1.21 (95% CI 0.56–2.61); P = 0.62; I 2  = 30%]. A meta-analysis of eight randomized controlled trials comparing metformin (n = 838) with insulin (n = 836), however, showed a reduced risk of pre-eclampsia with metformin [RR, 0.68 (95% CI 0.48–0.95); P = 0.02; I 2  = 0%]. No heterogeneity was present in the metformin vs. insulin analysis of randomized controlled trials, whereas high levels of heterogeneity were present in studies comparing metformin with placebo/control. Pre-eclampsia was a secondary outcome in most of the studies. The mean weight gain from time of enrolment to delivery was lower in the metformin group (P = 0.05, metformin vs. placebo; P = 0.004, metformin vs. insulin). Conclusions: In studies randomizing pregnant women to glucose-lowering therapy, metformin was associated with lower gestational weight gain and a lower risk of pre-eclampsia compared with insulin.
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