Is a vegetarian diet safe to follow during pregnancy? A systematic review and meta-analysis of observational studies.

Background

Whether a vegetarian diet is appropriate for pregnancy remains unclear.

Objective

This study aimed to determine the association between vegetarian diet during pregnancy and various maternal-fetal outcomes. Method: PubMed-Medline, EMBASE, and Cochrane Library databases were searched for relevant articles published by August 30, 2017. Quantitative data were analyzed by a random-effects model with pooled odds ratios or weighted mean difference (WMD) and 95% confidence interval as aggregate estimations.

Results

A total of 19 observational studies were identified for each of meta-analysis and narrative review. The overall estimated relation between vegetarian pregnancy and low birth weight (LBW) was marginally significant (1.27 (0.98, 1.65), P = 0.07, I2=0%). Asian (India/Nepal) vegetarian mothers exhibited increased risks to deliver a baby with LBW (1.33 (1.01, 1.76), P = 0.04, I2=0%). However, the WMD of neonatal birth weight in five studies suggested no difference between vegetarians and omnivores. Given the high heterogeneity of the included studies, lack of high-quality evidence, and limited studies included for each category, we failed to reach conclusive results regarding the risks of hypospadias, intrauterine growth retardation, maternal anemia, and gestational diabetes mellitus.

Conclusion

Asian vegetarian mothers presented increased risks to deliver babies with LBW than those of omnivores. Large-scale prospective studies focusing on pre- and/or early gestational nutrition will help clarify the correlation between vegetarian diet and various pregnancy outcomes.