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.