There is considerable difference of opinion about the criteria for the diagnosis of megaloblastic anaemia during pregnancy and about the value of laboratory tests both as an aid in diagnosis and as an indication of the nature of the ‘deficiency’. The urinary excretion of form-iminoglutamic acid as a test for folic acid function in megaloblastic anaemia of pregnancy has been found to be of great value by Hibbard (1964) and of little value by others (Chanarin, Rothman and Watson-Williams, 1963; Hansen, 1964; Chisholm and Sharp, 1964). Megaloblastic anaemia in pregnancy may be found at a time when the serum L. casei (Folate) level is within the normal range (Waters and Mollin, 1961; Chanarin, 1964; Spray, 1964) but Ball and Giles (1964) find the estimation of the so-called ‘labile’ serum L. casei activity of value. The data published by Izak, Rachmilewitz, Sadovsky, Bercovici, Aronowitch and Grossowicz (1961) indicate that assay of whole blood folic acid does not permit a distinction in pregnancy between iron deficiency anaemia and megaloblastic anaemia; however, Hansen (1964) found that whole blood folate was abnormally low in those patients with clinically significant folate deficiency in pregnancy.

Recently we have studied the effect of various dietary supplements on the results of tests of folic acid function in pregnancy. These tests were carried out at regular intervals throughout pregnancy. Bone marrow samples were obtained in the last few weeks of pregnancy in 43 women in this study. Haemopoiesis was megaloblastic in 15 of these women and was normo-blastic in the remaining 28. It is the purpose of this paper to compare the observations throughout pregnancy in the group who developed megaloblastic anaemia with those in women in whom haemopoiesis remained normoblastic.