THE MINIMAL adult requirement for folic acid is estimated to be 50μg per day.1,2 It is generally believed that requirements for folic acid are increased during pregnancy 3; however, carefully documented data are lacking. In previous studies which measured the response to folic acid therapy in megaloblastic anemia of pregnancy,4-7 the folate content of diets was not quantitated and usually "titrated" 7 doses of folic acid were not administered. Recently investigations were initiated to study the requirements of folic acid during pregnancy. Some of the preliminary observations are described.
—Standard hematologic tests, including the preparation of bone marrow for examination, were performed with established techniques.8-10 The quantity of vitamin B12 in serum was assayed with Euglena gracilis.11 All assays of folate activity were performed with Lactobacillus casei. A modification12 of the method of Herbert13 was used for measuring serum folate activity. Whole-blood folate activity was determined by