(OR21-05-23) Maternal Adherence to Vegetarian Diets and Perinatal Health: Findings From Two British Birth Cohort Studies

Objectives: To examine the associations between adherence to vegetarian (V) diets during pregnancy and perinatal health in the Avon Longitudinal Study of Parents And Children (ALSPAC) and Born in Bradford (BiB) study.

Methods: Food frequency questionnaire data were available in 11852 and 3871 singleton pregnancies in ALSPAC and BiB, respectively. Due to small sample sizes, semi-V, pesco-V, lacto-ovo-V, and vegans were combined as broadly defined V (N = 614 [5.2%] in ALSPAC; N = 139 [3.6%] in BiB). A total of 20 maternal, pregnancy, and offspring outcomes were examined. Results from each study were meta-analysed with fixed-effects models and corrected for multiple testing using 5% false discovery rate (FDR). Analyses were adjusted for maternal demographic, lifestyle, and nutrition-related factors. Residual confounding by socioeconomic position (SEP) as indicated by maternal education attainment was explored by comparing results between BiB mothers of European (N = 1955) and non-European (N = 1912) ancestry since maternal education attainment was associated with V-diets adherence in the former but not the latter group.

Results: In both cohorts, higher adherence to V-diets was consistently associated with increased odds of maternal anaemia during pregnancy (OR: 1.61 [95% CI: 1.24, 2.10], P<sub>FDR = 0.006, I² = 0%) and longer breastfeeding (BF) (BF ≥ 6 months OR: 1.66 [1.33, 2.06], P<sub>FDR  < 0.001, I² = 0%). The increased risk of maternal anaemia was lower in women with iron supplementation compared to those without (OR: 1.29 [0.91, 1.82], I² = 0% vs. 2.36 [1.55, 3.59], I² = 0%). In BiB, the association with BF was fully attenuated in women of non-European (OR: 1.09 [0.65, 1.82]) compared with European (2.62 [1.67, 4.11]) ancestry. No associations were observed with other perinatal outcomes, e.g., hypertensive disorders of pregnancy, C-section, preterm birth, birth weight, Apgar scores, etc.

Conclusions: Evidence from two cohorts consistently showed a higher risk of maternal anaemia associated with V-diets adherence in pregnancy, which was attenuated among iron supplement users; the observed association with BF seemed to reflect residual confounding by SEP. While our findings support the safety of V-diets for pregnancy and fetal health, we are replicating these findings in larger samples and exploring potential differences between V-subgroups.

Funding Sources: Wellcome Trust