EP17.08: The association between maternal vitamin B12 insufficiency and obesity: a systematic review

Abstract

The rising rates of obesity in pregnancy together with the paradox of nutritional deficiencies in these women have important implications for maternal and fetal well being. Specifically, the micronutrients B12 and folate are required to support the increased demands of the fetus in pregnancy. Deficiencies in these micronutrients can lead to increased maternal adiposity, maternal and offspring insulin resistance and adverse lipid profile in neonates. This review aims to assess existing evidence linking maternal vitamin B12 deficiency with obesity. Inclusion criteria was body mass index (BMI) greater than or equal to 30 kg/m2, non diabetic, pregnant population. The outcome was vitamin B12 level measured at any gestational age. We considered observational studies, randomised control trials and case control studies. We searched Medline, Embase, CINAHL and The Cochrane Library database. Two reviewers independently extracted data from relevant studies. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) statement. Of 366 articles identified, seven met inclusion criteria. Most studies were observational, with one case control study. There was consistent evidence linking maternal obesity with low vitamin B12 levels (defined as <150 pmol/L). Most studies adjusted for potential confounders, such as maternal demographics, lifestyle factors, pregnancy related factors and hemodilution. BMI remained a significant negative predictor of low vitamin B12. In the case control study, third trimester vitamin B12 insufficiency was associated with a 2.4 times increased odds of first trimester obesity. As the prevalence of maternal obesity is rapidly increasing, the implications of low vitamin B12 on maternal and fetal health need to be considered. Further longitudinal cohort studies are needed to understand the mechanisms between vitamin B12 and obesity, to identify any possible causal relationship and therefore potentially offer simple interventions to improve maternal and offspring health.