Aims: Vitamin B12 insufficiency has been linked with adiposity and insulin resistance. A clinical study from India showed that B12 insufficiency in pregnancy was associated with higher risk of gestational diabetes (GDM), mediated by maternal BMI. It is not known whether the same association exists among pregnant women in the UK.
Methods: A retrospective study was done on women attending our antenatal clinic from 20102013. Information including maternal demographics, first trimester BMI, B12, folate and glucose were collected and multivariate regression models applied.
Results: Two hundred and ninty four women (132 GDM, 162 controls) who had B12 levels checked in the early third trimester were included. Overall, 26.9% had B12 values <150 pmol/l. GDM mothers were older, more obese and had significantly lower mean B12 values than controls (184 vs 225 pmol/l, P=0.03) with similar folate levels. In all women, first trimester BMI had a significant negative correlation with third trimester B12 (r=−0.21, P<0.001). Linear regression showed that first trimester BMI was the only significant predictor of B12 (β=−0.2, P=0.002), after adjusting for age, parity, ethnicity, folate and gestation. Women in the lowest B12 tertile had significantly higher odds of a diagnosis of GDM than those in the highest tertile (AOR: 2.45, 95% CI 1.24, 4.84), after adjusting for BMI and other variables as above.
Conclusion: This study confirms, for the first time in a UK population, that obese pregnant women are at risk of B12 insufficiency, which in turn is associated with over two-times higher probability of GDM. Further longitudinal studies are urgently needed to determine whether early pregnancy B12 insufficiency predicts the onset of GDM and establish the mechanisms underlying the link between insulin resistance and B12.