Women who use oral contraceptives have impaired folate metabolism as shown by slightly but significantly lower levels of folate in the serum and the erythrocytes and an increased urinary excretion of formiminoglutamic acid. The vitamin B12 level in their serum is also significantly lower than that of control groups. However, there is no evidence of tissue depletion of vitamin B12 associated with the use of oral contraceptives. The causes and clinical significance of the impairment of folate and vitamin B12 metabolism in these women is discussed in this review of the literature. Clinicians are advised to ensure that women who shop taking "the pill" because they wish to conceive have adequate folate stores before becoming pregnant.
PIP: The effects of oral contraception (OC) on folate and vitamin B12 metabolism are a subject of much controversy. Many studies indicate that OCs impair folate metabolsim and produce some degree of folate depletion, as demonstrated by slight but significant lower levels of folate in the serum and the erythrocytes, and by an increased urinary excretion of formiminoglutamic acid. These effects are unlikely to cause anemia or megalobastic changes in women who have a good dietary intake of folate. Since pregnant women are predisposed to the development of folate deficiency, it would be necessary when stopping the pill for desire of pregnancy to take folate supplements before becoming pregnant. OCs may also produce a low serum level of vitamin B12; this effect, however, is not associated with evidence of tissue depletion of vitamin B12, and does not have any great clinical significance; the effect may also be caused by vitamin B12 malabsorption rather than by OC treatment.