Objective: To determine the effect of a maternal vegan diet on pregnancy outcome.
Study design: This is a prospective observational study. Women with a singleton pregnancy who maintained the same diet prior to, and throughout current pregnancy were enrolled. Stratification was performed according to diet type: vegans, lacto-ovo-vegetarians, fish-eaters, and omnivores.
Results: Overall, 273 women were enrolled, of them, 112 omnivores, 37 fish-eaters, 64 lacto-ovo-vegetarians, and 60 vegans. The vegan diet was significantly associated with an increased risk of small-for-gestational-age newborns compared only to an omnivore diet (RR = 5.9, 95% CI, 1.2-21.8). The incidence of preterm birth was similar in all groups. Vegans had lower birthweight compared to lacto-ovo-vegetarians (3015 ± 420 g vs. 3285 ± 482 g, P = 0.004), and to omnivores (3328 ± 495 g, P < 0.001), but not to fish-eaters. Vegans also had a lower mean gestational weight gain compared only to omnivores (11.6 ± 4.2 kg vs. 14.3 ± 4.6 kg, P = 0.001).
Conclusion: The vegan diet is associated with an increased risk for small-for-gestational-age newborns and lower birthweight.