Maternal vitamin B-12 status is negatively related to high plasma folate in early pregnancy

Abstract Number Theme Presentation Type Cover Approved
0599 Prevalence and risk factors for micronutrient status(deficiency, overload) Poster Not Approved


Abstract Content


To characterize changes in vitamin B-12 (B-12) and folate status biomarkers across pregnancy and to assess the influence of high plasma folate on B-12 status.


Prospective cohort comprising 299 women followed during the three trimesters of pregnancy in a primary health center in Rio de Janeiro, Brazil. Plasma concentrations of total B-12, total homocysteine (tHcy), methylmalonic acid (MMA) and folate were measured. The combined B-12 status indicator (cB-12) was calculated from B-12/tHcy*MMA corrected for age and folate. Longitudinal linear mixed-effect regression models were used to assess changes across time.


In the 1st trimester, 3.1% and 19.6% presented low (B12<148 pmol/L) and marginal B-12 (148-221 pmol/L) while 2.2% and 13.3% had low (<10 nmol/L) and high (>45 nmol/L) plasma folate. Mean (SD) plasma B-12 concentrations (pmol/L) decreased from 317.3 (116.7) in the 1st to 259.1 (134.6) in the 2nd to 239.1 (83.5) in the 3rd trimester (ß=-3.82, p<0.001). tHcy (µmol/L) presented a U-shaped curve [6.3 (1.7), 5.1 (1.2) and 5.6 (1.5). MMA (nmol/L) increased [176.5 (104.1), 197.0 (117.0) and 249.0 (153.6) (ß=2.60, p=0.02)]. Overall B-12 status (cB-12) declined across pregnancy (ß=-0.008, p<0.001). Plasma folate (nmol/L) also decreased [27.2 (10.4), 24.7 (9.6) and 23.9 (9.6) (ß=-0.13, p=0.001)]. Women in the lowest tertile of cB-12 and upper tertile (mean=39.2 nmol/L) of plasma folate in the 1st trimester had worse B-12 status across pregnancy (p<0.001) compared with women in the lowest tertile of both cB-12 and plasma folate (mean=16.3 nmol/L) such that the prevalence of B-12 <221 pmol/L in 1st, 2nd and 3rd trimester= 58%, 79% and 67%, respectively in the group with first-trimester low B-12 and high folate status and 39%, 63% and 58%, respectively in the group with first-trimester low B-12 and normal folate status.


B-12 and folate status in apparently healthy pregnant women is characterized by a physiological decrease across trimesters which is accentuated in women with low B-12 status and high plasma folate in early pregnancy.

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