Effect of Folic Acid and Vitamin B12 Supplementation on Tests of Folate and Vitamin B12 Nutrition in Pregnancy

Abstract

The effect of folic acid and vitamin B₁₂ supplements in pregnant subjects subsisting on a good Western type diet has been studied. The serum L. casei folate activity, serum vitamin B₁₂ concentration, urinary FIGLU excretion after histidine loading, and the hemoglobin and hematocrit have been determined at regular intervals in subjects given supplements of either iron, iron and folic acid, or iron, folic acid and vitamin B₁₂. Urinary FIGLU excretion was highest in early pregnancy, and then decreased steadily up to the time of delivery. In patients receiving folic acid, FIGLU excretion was significantly reduced. While FIGLU excretion after histidine loading in pregnant subjects is related to physiologic changes in histidine metabolism during pregnancy, increased excretion in late pregnancy probably reflects folate deficiency. The serum L. casei folate level showed little change during pregnancy, but the administration of folic acid resulted in a prompt and significant increase in the serum values. The serum vitamin B₁₂ concentration decreased markedly during pregnancy and increased again after delivery; this pattern was not changed by vitamin B₁₂ supplementation. The administration of folic acid and vitamnin B₁₂ to groups of pregnant subjects receiving iron did not result in a significant increase in the mean hemoglobin or hematocrit values.