The effect of oral contraceptive therapy and of pregnancy on serum folate levels of rural Sri Lankan women

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.

Investigation of folate intake and metabolism in women who have had two pregnancies complicated by neural tube defects

OBJECT

To investigate folate intake and blood levels of folic acid and vitamin C in women with and without a history of two NTD-affected pregnancies and to measure the increase in serum folate following ingestion of orange juice.

SUBJECTS

Sixteen women with a history of two NTD-affected infants and 16 controls with no such history, none of whom were either pregnant or taking vitamin supplements. The orange juice loading test was carried out on eight matched pairs.

MAIN OUTCOME MEASURES

Dietary intake of folate was assessed by questionnaire and blood levels of folate and vitamin C were measured.

RESULTS

There was no evidence of decreased intake of folate in subjects who had had two NTD-affected pregnancies. In controls, both serum and red cell folate showed significant correlation with dietary folate, while in subjects there was no such correlation. Subjects also had smaller increases in serum folate following an oral load than controls, although the differences were not significant.

CONCLUSION

Women who have had two NTD-affected pregnancies may have defective folate metabolism. Further investigations on short term utilisation of ingested food folates in these women are required.

An investigation on the influence of steroidal contraceptives on milk lipid and fatty acids in Hungary and Thailand. WHO Special Programme of Research, Development and Research Training in Human Reproduction. Task Force on oral contraceptives

A double-blind clinical trial to examine the effects of oral and long-acting injectable contraceptive steroids on milk lipid and its fatty acid content has been done in Szeged, Hungary, and Khon-Kaen, Thailand. In Szeged, a combined and a progestin-only pill did not significantly alter total milk lipid. In Khon-Kaen, treatment with the combined pill was followed by a significant increase in the proportion of milk lipid. In the group treated with the long-acting injectable contraceptive, depot-medroxyprogesterone acetate (DMPA), the milk lipid decreased significantly in the first six weeks in comparison with the control group and the individual pretreatment values. A similar but weaker effect was noticed with the progestin-only pill in Khon-Kaen. Few consistently significant differences were found in the shorter chain fatty acids (myristic, lauric and palmitic acids) during treatment. The percentage proportions were increased during the combined pill treatment in Szeged and Khon-Kaen, and reduced in DMPA and progestin-only treatment in Khon-Kaen milks. The possibility that these reflected a response to a milk volume decrease in the combined pill treatment and a reduction in milk lipid synthesis in association with DMPA and the progestin-only pill is discussed. In Khon-Kaen, linoleic acid (which is not synthesized in the body) was increased by comparison with the controls, as a percentage proportion of the fatty acids in the progestin-only and DMPA groups. Calculation of the amounts of linoleic acid per litre of milk revealed that there had been a significant decrease of linoleic, eicosadienoic, dihommo-gamma-linolenic, arachidonic, docosatetraenoic acids in the w6 family and alpha-linolenic acid in the w3 family in the first two post-treatment visits (3 and 4). This reduction in essential fatty acid output follows the reduction in milk volume. In Khon-Kaen, the combined pill group showed a significant decrease compared with the controls, in the proportions of dihommo-gamma-linolenic acid. The difference in response of the mothers in Khon-Kaen and Szeged is discussed in relation to their different nutritional backgrounds.