A longitudinal study of maternal folate and vitamin B12 status in pregnancy and postpartum, with the same infant markers at 6 months of age.

Folate and vitamin B12 are involved in homocysteine metabolism and are critical to the methylation of DNA. We aimed to assess plasma vitamin B12 (pB12), plasma folate (pFol), and red cell folate (rcFol) in women and their infants during pregnancy and after birth. Maternal biomarkers were tested as predictors of infant biomarkers, including plasma homocysteine (pHcy), at age 6 months. Participants (n = 153) were recruited at the John Hunter Hospital, Australia. Maternal fasting blood samples were collected at 20 and 36 weeks gestation, and at 14 and 27 weeks postpartum. Fifty healthy, term infants provided non-fasting samples at age 6 months. Plasma homocysteine data were available for 16 infants at age 6 months. Maternal pB12 concentrations fell by 16% from 20 to 36 weeks gestation, but had recovered by 14 weeks postpartum. Maternal rcFol concentrations fell by 31% from 20 weeks gestation to 27 weeks postpartum. Infants breastfed at 6 months had lower pB12 (median 159 vs. 402 pmol/L, n = 23 vs. 18, P < 0.01) and folate (median folate z-score -0.58 vs. 0.85, n = 23 vs. 17, P < 0.01), and higher pHcy (median 11.9 vs. 7.3 μmol/L, n = 8 vs. 6, P < 0.01), than those on infant formula. Maternal pregnancy pFol, but not pB12, inversely predicted infant pHcy, after adjustment for the infant's current pB12 (P = 0.04). Changes in maternal B12 and folate occur during pregnancy and after birth. Infant homocysteine metabolism may be regulated through maternal folate concentrations during pregnancy and postnatal feeding.