Folate and vitamin B12 status of women in Newfoundland at their first prenatal visit.

BACKGROUND: Newfoundland has one of the highest rates of neural tube defects in North America. Given the association between low maternal folic acid levels and neural tube defects, a cross-sectional study was conducted to obtain base-line data on the folate and vitamin B12 status of a sample of women in Newfoundland who were pregnant. METHODS: Blood samples were collected between August 1996 and July 1997 from 1424 pregnant women in Newfoundland during the first prenatal visit (at approximately 16 weeks' gestation); this represented approximately 25% of the women in Newfoundland who were pregnant during this period. The samples were analysed for serum folate, vitamin B12, red blood cell folate and homocysteine. RESULTS: Median values for serum folate, red blood cell folate and serum vitamin B12 were 25 nmol/L, 650 nmol/L and 180 pmol/L, respectively. On the basis of the interpretive criteria used for red blood cell folate status, 157 (11.0%) of the 1424 women were deficient (< 340 nmol/L) and a further 180 (12.6%) were classified as indeterminate (340-420 nmol/L). Serum homocysteine levels, measured in subsets of the red blood cell folate status groups, supported the inadequate folate status. Serum vitamin B12 levels of 621 (43.6%) women were classified as deficient or marginal; however, the validity of the interpretive criteria for pregnant women is questionable. INTERPRETATION: A large proportion of pregnant women surveyed in Newfoundland in 1997 had low red blood cell folate levels.