Recent studies implicate maternal gestational diabetes mellitus (GDM) in differential methylation of infant DNA. Folate and vitamin B12 play a role in DNA methylation, and these vitamins may also influence GDM risk. The aims of this study were to determine folate and vitamin B12 status in obese pregnant women and investigate associations between folate and vitamin B12 status, maternal dysglycaemia and neonatal DNA methylation at cytosine-phosphate-guanine sites previously observed to be associated with dysglycaemia. Obese pregnant women who participated in the UK Pregnancies Better Eating and Activity Trial were included. Serum folate and vitamin B12 were measured at the oral glucose tolerance test (OGTT) visit. Cord blood DNA methylation was assessed using the Infinium MethylationEPIC BeadChip. Regression models with adjustment for confounders were used to examine associations. Of the 951 women included, 356 (37.4%) were vitamin B12 deficient, and 44 (4.6%) were folate deficient. Two-hundred and seventy-one women (28%) developed GDM. Folate and vitamin B12 concentrations were not associated with neonatal DNA methylation. Higher folate was positively associated with 1-h plasma glucose after OGTT (β = 0.031, 95% CI 0.001–0.061, p = 0.045). There was no relationship between vitamin B12 and glucose concentrations post OGTT or between folate or vitamin B12 and GDM. In summary, we found no evidence to link folate and vitamin B12 status with the differential methylation of neonatal DNA previously observed in association with dysglycaemia. We add to the evidence that folate status may be related to maternal glucose homoeostasis although replication in other maternal cohorts is required for validation.

In the UK 21% of pregnant women are categorised as obese(1). Women who enter pregnancy with a high body mass index (BMI) are at greater risk of gestational weight gain (GWG) above that recommended by the Institute of Medicine (IOM) and are less likely to return to their pre-pregnancy weight compared to women with a healthy BMI(2). Pregnancy can therefore alter a woman's weight gain trajectory across the life course, through retention of gestational weight gained. Given the increase in prevalence of obesity among women of reproductive age, the aim of this study was to identify antenatal and postnatal modifiable determinants associated with successful postpartum weight loss in women who participated in UPBEAT; a multi-centre randomised controlled trial comparing a lifestyle intervention of diet and physical activity to standard care during pregnancy.

710 women completed the 6-month postpartum follow-up visit, 464 (65%) of which provided complete data for the analysis. Using regression analysis, we examined the relationship between postpartum weight retention (PPWR; calculated by subtracting pre-pregnancy weight from six-month postpartum weight) and modifiable determinants including: reported glycaemic index and smoking status at baseline (15–18 weeks’ gestation), GWG within the IOM recommendations, self-reported postpartum physical activity (categorised as low, moderate or high) and mode of infant feeding (breastfed, formula or mixed). Women were excluded if they gave birth < 37 weeks gestation or they were pregnant at the 6-month visit. Results were adjusted for age, BMI, ethnicity, socio-economic status, parity and randomisation arm.

In this cohort of obese women 52% were at or below their pre-pregnancy weight by 6 months postpartum. Overall, there was a reduction in PPWR of -0.23 ± 6.7 kg [-23.5 to 23.0 kg]. In an adjusted multiple regression model, women who breastfed for ≥ 4months, had moderate or high levels of physical activity and appropriate GWG, were more likely to be at or below their pre-pregnancy weight by 6-months postpartum (all p < 0.02). In a mutually-adjusted multivariate model, for each additional factor women lost a further -1.5 kg (95%CI -2.3 to -0.68; p < 0.001) compared to their pre-pregnancy weight.

This study has shown that there is an incremental association with postpartum weight loss and the identified modifiable determinants. These findings support initiatives which target any or all these factors during the antenatal and postnatal periods to help support women with returning to their pre-pregnancy weight.