Strict vegetarian diet and pregnancy outcomes: A systematic review and meta-analysis.

Introduction: The increasing adoption of strict vegetarian diets during pregnancy has raised concerns about their effects on maternal and neonatal outcomes. This systematic review and meta-analysis aimed to assess the impact of strict vegetarian diets on key pregnancy outcomes, including neonatal birth weight, small-for-gestational-age (SGA) infants, gestational diabetes mellitus (GDM), hypertensive disorders, and gestational weight gain (GWG).

Methods: A comprehensive literature search across multiple databases yielded eight studies from various countries, involving a total of 72,284 participants. Primary outcomes included neonatal birth weight, SGA, preterm birth, GDM, and maternal hypertensive disorders.

Results: The meta-analysis found that strict vegetarian diets were significantly associated with an increased risk of delivering SGA infants, with a pooled odds ratio (OR) of 2.71 (95 % confidence interval [CI]: 1.24 to 5.95;  = 0.01). Additionally, infants born to strict vegetarian mothers had lower birth weights, with some studies reporting a mean difference of 240g compared to omnivores. For GDM, no significant differences were found between strict vegetarians and omnivores, with a pooled OR of 0.64 (95 % CI: 0.37 to 1.11;  = 0.11). While vegans showed lower gestational weight gain and reduced risk of excessive weight gain, there was considerable heterogeneity in results regarding hypertensive disorders and preterm birth.

Conclusions: Strict vegetarian diets during pregnancy are associated with an increased risk of SGA infants and lower birth weights. To mitigate these risks, specific dietary guidelines emphasizing adequate intake of critical nutrients such as vitamin B12, iron, omega-3 fatty acids, and iodine should be developed. Supplementation and tailored dietary counseling, incorporating fortified foods and plant-based sources like legumes, nuts, seeds, and algae-derived omega-3, are essential to ensure maternal and neonatal health. Further research is necessary to refine these guidelines and explore their impact on diverse populations.