Correlation of folate metabolism and socioeconomic status in pregnancy and in patients taking oral contraceptives

Association Between Use of Oral Contraceptives and Folate Status: A Systematic Review and Meta-Analysis

OBJECTIVE

To conduct a systematic review and meta-analysis of the effect of oral contraceptive use on plasma and red blood cell (RBC) folate concentrations.

METHODS

We searched Medline, EMBASE, Web of Science, and the Cochrane library for human studies published from inception to June 2013 evaluating oral contraceptive use and folate status. Case-control studies, cohort studies, and clinical trials were included. A random-effects model of outcomes was used for the meta-analysis.

RESULTS

A total of 2831 women in 17 studies were included in the analysis. In those whose plasma folate concentrations were available, there was a significant folate-lowering effect of oral contraceptives observed (mean reduction 1.27 µg/L; 95% CI 1.85 to 0.69, P < 0.001). Similarly, after analyzing data from 1389 women in 12 studies whose RBC folate concentrations were available, significantly lower folate status was observed among oral contraceptive users (mean reduction 59.32 µg/L; 95% CI 58.03 to 23.04, P < 0.001).

CONCLUSION

Because of the reduction in blood folate concentrations associated with the use of oral contraceptives, it is critical for women of childbearing age to continue folate supplementation during oral contraceptive use.

Effect of oral contraceptives on blood folate levels in pregnancy

An investigation was carried out to assess residual effects of oral contraceptives on the folate status of pregnant women who had discontinued intake of these drugs within six months of conception. The sample population of middle class women consisted of users and nonusers of oral contraceptives of similar age groups. Subgroups were those studied initially during the summer (May to July) or winter (October to January). Red blood cell folate values showed seasonal variability and were lower in the winter months. Oral contraceptive users had lower plasma and red blood cell folate values than did the respective control subjects. Red blood cell folate values were more affected by previous drug use in the winter group than in the summer group. Dietary folate was found to have a significant effect on plasma and red cell folate; such for any one level of intake, blood folate values were significantly lower in oral contraceptive users.

Folic acid deficiency in the United States: folate assays in a prenatal clinic

Tissue deficiency of folic acid, as measured by a red cell folate level below 150 ng. per milliliter, was present in 16 per cent of 110 sequential pregnant women at the time of their first prenatal visit to a municipal clinic. A further 14 per cent of subjects had red cell folate levels in the range "suggestive but not conclusive for tissue folate depletion" (150 to 199 ng. per milliliter). All of the subjects were from low-income families in New York City and most were black or of Puerto Rican origin. Serum folate levels showed good general correlation with red cell folate but were of less value as a diagnostic test, since they were below the lower limit of normal in 64 per cent of subjects, including many subjects who did not yet have low tissue folate. In contrast to their value in other folate deficiency states, neutrophil lobe counts showed no correlation with serum or red cell folate levels in pregnancy and thus appeared of little diagnostic value in pregnancy. It is suggested that surveys of folate deficiency in other pregnant population groups in the United States be carried out. These results support the recommendations of the Committee on Maternal Nutrition and the Committee on Dietary Allowances of the Food and Nutrition Board, National Research Council (U.S.A.) that folic acid supplements (200 to 400 mug per day) should be taken throughout pregnancy.