Folic acid and vitamin B12 levels in pregnancy and their relation to megaloblastic anaemia

Abstract

SYNOPSIS There is a significant fall in the serum folic acid level during pregnancy, reaching its lowest level at term. This is most pronounced in twin pregnancies. A similar but less spectacular fall occurs in the vitamin B12 concentration.In megaloblastic anaemia both folic acid and vitamin B12 levels are lower than in other pregnant women. The degree of megaloblastic change in the bone marrow, as measured by the type and number of megaloblasts, is reflected in the vitamin levels, cases with florid megaloblastosis showing the most marked depression of vitamin B12 and folic acid activity.Although there is a significant difference in the mean folic acid levels between megaloblastic and normoblastic pregnant women, a considerable overlap exists between individual values in the two groups. When the labile folic-acid factor is determined separately the test becomes much more specific. In the present series, all cases of megaloblastic anaemia yielded labile-factor levels below 1 0 m,ug. per ml., while a similar value was encountered in only one of 35 normal pregnancies.In five women with megaloblastic anaemia the vitamin B12 concentration was less than 100 ,u,ug. per ml. but rose to normal levels on folic acid therapy alone.

Prevalence of vitamin B-12 insufficiency during pregnancy and its effect on offspring birth weight: a systematic review and meta-analysis

“…There were 6 studies identified from the full-text review that reported vitamin B-12 insufficiency rates during pregnancy but without specifying a trimester (43)(44)(45)(46) or clearly stating the number of women sampled per trimester (47,48). These studies were not included in further analysis.…”

Investigation of folic acid requirements in pregnancy.

“…The immediate postpartum period was chosen for purposes of measuring the serum folate, since the lowest levels associated with pregnancy are reached at this time (Solomons et al, 1962;Ball and Giles, 1964;Chanarin et al, 1965 ;Edelstein et al, 1966), when the body stores have presumably been put to the maximum strain as a result of both foetal demands and the variable blood loss of delivery. From a practical point of view it would be valueless to establish a suitable folic acid supplement which would sustain a normal folic acid status throughout pregnancy but perhaps fail to do so in the puerperium, which is when a high proportion of megaloblastic anaemias of pregnancy first become manifest.…”

How I treat anemia in pregnancy: iron, cobalamin, and folate

“…A "physiologic" decline in cobalamin is seen in up to 20% of pregnant women that is indistinguishable from frank deficiency using routine laboratory studies. 79,81,82 Holotranscobalamin (biologically active cobalamin bound to transcobalamin) does not decline in pregnancy and has been suggested as a marker for cobalamin deficiency in pregnancy. 83 Holotranscobalamin is not available for clinical use.…”