Abstract
Aims/hypothesisThe prevalence of gestational diabetes mellitus (GDM) is increasing worldwide in all ethnic groups. Low vitamin B12 and low/high folate levels may contribute to GDM risk, but there is conflicting evidence. Our aim is to assess the relationships of early pregnancy vitamin B12 and folate levels with the risk of GDM status at 26–28 weeks of gestation.MethodsThis was a prospective, multi-centre, multi-ethnic cohort study (n = 4746) in the UK. Participants who were eligible to be selectively screened as per the National Institute for Health and Care Excellence (NICE) criteria were included in the study.ResultsGDM prevalence was 12.5% by NICE and 14.7% by International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. Folate deficiency (1.3%) was rare but B12 insufficiency (42.3% at <220 pmol/l) and folate excess (36.5%) were common in early pregnancy. Early pregnancy median B12 levels were lower, and folate levels higher, in women who were diagnosed with GDM at 26–28 weeks. B12 was negatively associated with fasting plasma glucose (1 SD: −0.06 mmol/l; 95% CI −0.04, −0.08; p < 0.0001) and 2 h plasma glucose levels (−0.07 mmol/l; 95% CI −0.02, −0.12; p = 0.004). Higher B12 was associated with 14.4% lower RR of IADPSG-GDM (0.856; 95% CI 0.786, 0.933; p = 0.0004) after adjusting for key confounders (age, parity, smoking status, ethnicity, family history, household income and folate status). Approximately half of this association was mediated through BMI. Folate was positively associated with 2 h plasma glucose levels (0.08 mmol/l; 95% CI 0.04, 0.13; p = 0.0005) but its relationship with fasting plasma glucose was U-shaped (quadratic β: 0.011; p = 0.05). Higher folate was associated with 11% higher RR of IADPSG-GDM (adjusted RR 1.11; 95% CI 1.036, 1.182; p = 0.002) (age, parity, smoking status, ethnicity, family history, household income and B12 status). Although no interactions were observed for B12 and folate (as continuous variables) with glucose levels and GDM risk, a low B12–high folate combination was associated with higher blood glucose level and risk of IADPSG-GDM (adjusted RR 1.742; 95% CI 1.226, 2.437; p = 0.003).Conclusions/interpretationB12 insufficiency and folate excess were common in early pregnancy. Low B12 and high folate levels in early pregnancy were associated with small but statistically significant changes in maternal blood glucose level and higher RR of GDM. Our findings warrant additional studies on the role of unmetabolised folic acid in glucose metabolism and investigating the effect of optimising early pregnancy or pre-conception B12 and folate levels on subsequent hyperglycaemia.Trial registration:ClinicalTrials.gov NCT03008824.Graphical abstract
Highlights
Gestational diabetes mellitus (GDM) is a common medical disorder in pregnancy, estimated to affect more than 20 million pregnancies worldwide, and causes significant shortand long-term consequences to both the women and their offspring [1]
The purpose of our study is to examine the relationships of B12, folate and total homocysteine (tHcy) levels in early pregnancy with the glucose levels and risk of GDM in late pregnancy, in a large, multi-ethnic, prospective cohort study
While household income was unrelated to B12 levels, higher income was associated with higher folate and lower tHcy levels
Summary
Gestational diabetes mellitus (GDM) is a common medical disorder in pregnancy, estimated to affect more than 20 million pregnancies worldwide, and causes significant shortand long-term consequences to both the women and their offspring [1]. While management of GDM reduces the short-term complications, it does not abolish them completely [2, 3]. Adverse effects for the offspring may have already happened prior to the diagnosis of GDM [4,5,6]. Prevention of GDM would be a better approach to reduce adverse outcomes in pregnant women and their offspring. This will require identifying and modifying risk factors before the diagnosis of GDM. Identification of other modifiable risk factors that contribute to GDM risk is needed
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