Early pregnancy folate-cobalamin interactions and their effects on cobalamin status and hematologic variables throughout pregnancy

Background

Periconception folic acid supplementation is widespread, but how it interacts with cobalamin status is rarely considered.

Objective

The aim of this study was to investigate whether first-trimester folate-cobalamin interactions affect pregnancy cobalamin status, hematologic variables, and pregnancy outcomes.

Design

In the longitudinal Reus-Tarragona Birth Cohort study from <12 gestational weeks throughout pregnancy, fasting plasma and red blood cell (RBC) folate, plasma cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), total homocysteine (tHcy), hemoglobin, mean cell volume (MCV), postglucose-load serum glucose, gestational hypertension, gestational age at birth, and birth weight were recorded in 563 participants.

Results

The highest plasma folate concentrations occurred in the first trimester when folic acid supplement use was extensive. Supplementation beyond the first trimester interacted with time of pregnancy on plasma folate, RBC folate, and tHcy throughout pregnancy (P-interaction <0.001). Plasma folate and RBC folate were higher and tHcy was lower in continued supplement users than in nonusers. Elevated plasma folate (≥30 nmol/L) occurred in 78.9% of women who exceeded the recommended 400 µg folic acid/d. First-trimester folate-cobalamin status interactions were associated with MMA (P-interaction <0.001) throughout pregnancy. When plasma cobalamin was suboptimal (≤221 pmol/L; n = 36), participants with elevated plasma folate (n = 11) had higher MMA concentrations than did those with nonelevated plasma folate (n = 23). First-trimester folate-MMA status interactions were associated with MCV throughout pregnancy (P-interaction <0.01) and with cord plasma holoTC (P-interaction <0.05). The mean difference (95% CI) in MCV (fL) between women with elevated and nonelevated plasma folate status was -2.12 (-3.71, -0.52) for top-quartile plasma MMA (≥0.139 µmol/L) and 0.60 (-0.39, 1.60) for plasma MMA <0.139 µmol/L. Cord plasma holoTC was higher in women with elevated compared with nonelevated plasma folate status only for MMA <0.139 µmol/L. Folate-cobalamin interactions were not associated with the other investigated outcomes.

Conclusion

First-trimester folate-cobalamin status interactions were associated with plasma MMA and MCV throughout pregnancy. This trial was registered at www.clinicaltrials.gov as NCT01778205.

Maternal Folate Status and the BHMT c.716G>A Polymorphism Affect the Betaine Dimethylglycine Pathway during Pregnancy

The effect of the betaine: homocysteine methyltransferase BHMT c.716G>A (G: guanosine; A: adenosine) single nucleotide polymorphism (SNP) on the BHMT pathway is unknown during pregnancy. We hypothesised that it impairs betaine to dimethylglycine conversion and that folate status modifies its effect. We studied 612 women from the Reus Tarragona Birth Cohort from ≤12 gestational weeks (GW) throughout pregnancy. The frequency of the variant BHMT c.716A allele was 30.8% (95% confidence interval (CI): 28.3, 33.5). In participants with normal-high plasma folate status (>13.4 nmol/L), least square geometric mean [95% CI] plasma dimethylglycine (pDMG, µmol/L) was lower in the GA (2.35 [2.23, 2.47]) versus GG (2.58 [2.46, 2.70]) genotype at ≤12 GW (p < 0.05) and in the GA (2.08 [1.97, 2.19]) and AA (1.94 [1.75, 2.16]) versus GG (2.29 [2.18, 2.40]) genotypes at 15 GW (p < 0.05). No differences in pDMG between genotypes were observed in participants with possible folate deficiency (≤13.4 nmol/L) (p for interactions at ≤12 GW: 0.023 and 15 GW: 0.038). PDMG was lower in participants with the AA versus GG genotype at 34 GW (2.01 [1.79, 2.25] versus 2.44 [2.16, 2.76] and at labour, 2.51 [2.39, 2.64] versus 3.00 [2.84, 3.18], (p < 0.01)). Possible deficiency compared to normal-high folate status was associated with higher pDMG in multiple linear regression analysis (β coefficients [SEM] ranging from 0.07 [0.04], p < 0.05 to 0.20 [0.04], p < 0.001 in models from early and mid-late pregnancy) and the AA compared to GG genotype was associated with lower pDMG (β coefficients [SEM] ranging from −0.11 [0.06], p = 0.055 to −0.23 [0.06], p < 0.001). Conclusion: During pregnancy, the BHMT pathway is affected by folate status and by the variant BHMT c.716A allele.