Vitamin B12 levels in pregnancy influence erythropoietin response to anemia.

OBJECTIVE: to discover whether vitamin B12 levels influence erythropoietin (EPO) response during pregnancy. STUDY DESIGN: 117 pregnant women after the 27th week were divided into three groups according to log vitamin B12 concentrations. EPO (by enzyme-linked immunosorbent assay), Hemoglobin (Hb) and medium corpuscular Hb concentration (MCHC) were measured in these patients. The tests used were: calculation of simple statistic, regression coefficient and t-independent test with level of significance. An exclusive partitioned cluster method (K-means procedure) was used. RESULTS: For the lowest vitamin B12 levels there is an unexpected lack of difference in plasma EPO levels between anemic and nonanemic patients. In fact EPO levels were high even in nonanemic women. The only parameter of the blood count that seems to change in relation to vitamin B12 concentration is the MCHC. CONCLUSIONS: These results suggest that low vitamin B12 levels inhibit the suppression of EPO response in nonanemic pregnant women probably through MCHC modifications.

The significance of the relationship between serum levels of cobalamin and MCHC during pregnancy.

Cobalamin concentration and mean corpuscular haemoglobin concentration (MCHC) were found to have highly significant inverse correlation with the weeks of pregnancy (respectively -.278 P < .0001 and .342 P < .00001) in 205 pregnant women. Among all haematometric parameters cobalamin concentrations during pregnancy only correlates with MCHC (P < .01). This datum seems to indicate an influence of B12 on erythropoiesis which adequate the concentration of haemoglobin to circulatory modifications of pregnant women.

Erythropoietin and transferrin concentrations during pregnancy in relation to hemoglobin levels.

Serum levels of erythropoietin (EPO) were assayed by ELISA at the same time as red blood cells (RBC), hemoglobin (Hb), hematocrit (Hct), serum iron and transferrin in 136 pregnant women, divided on the basis of hemoglobin values (> or < or = 10.5 g/dl) and weeks of pregnancy (< or > or = 27th week). In the overall population, a parallel increase with weeks of pregnancy was shown by serum concentrations of EPO expressed as a logarithm (multiple R = 0.367, P < 0.0001), and transferrin levels (multiple R = 0.529, P < 0.0001). It was found that EPO levels did not differ significantly between anemic and non-anemic patients before the 27th week, but the difference became highly significant (P < 0.01) after the 27th week in favour of anemic patients. Before the 27th week, the correlations between log EPO and RBC, Hct, Hb and iron were not significant, whereas the correlation between log EPO and transferrin was significant (P < 0.01); after the 27th week, the correlations and significance of the regression found were: log EPO vs Hb (Pearson coefficient = -0.384; P < 0.001), vs Hct (Pearson coefficient = -0.370; P < 0.01), vs transferrin (Pearson coefficient = 0.392; P < 0.0001), vs iron (Pearson coefficient = -0.274, P < 0.05). In the population divided according to Hb levels, the correlation was positive and significant in both groups between log EPO and transferrin (Hb > 10.5 g/dl: Pearson coefficient = 0.524, P < 0.0001; Hb < or = 10.5: Pearson coefficient = 0.614, P < 0.0001), but was inverse and significant only in the group with Hb < or = 10.5 g/dl between log EPO and serum iron (Pearson coefficient = -0.481, P < 0.01). The variations in EPO were related to Hb levels after the 27th week of pregnancy and were closely correlated with transferrin over the whole period. The physiological mechanism of these changes is discussed.

Iron balance in pregnancy in relation to anemia.

Blood levels of iron, transferrin and ferritin varied in the course of pregnancy (6th to 42nd week) in 136 women. Analysis of variance showed that the factor "weeks of pregnancy" (< or = 27 or > 27 weeks) was correlated differently with the variables "ferritin" and "iron" according to the presence or absence of anemia (Hb < or = or > or = 11 g/dl). In anemic women the correlation was significant (F-ratio = 5.90; P = 0.018) for iron (which decreased from initial low level until term) but not ferritin, whereas in non-anemic women the correlation was significant (F-ratio = 13.306; P = 0.0006) for ferritin (which decreased to less than 20 micrograms/ml around the 34th week) but not iron. In both anemic and non anemic subjects, transferrin levels increased with weeks of pregnancy. It is concluded that towards the end of pregnancy, some decrease in ferritin (> or = 15 micrograms/ml) is physiological, and in the absence of anemia (Hb > 11 g/dl) iron supplements are not necessary.