SERUM FERRITIN AND COBALAMIN IN GROWTH-RETARDED FETUSES

Objective To examine fetal and maternal serum cobalamin and ferritin concentrations pregnancies complicated by fetal growth retardation. Setting Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London. Design Cross sectional study. Subjects Fetal blood samples obtained by cordocentesis from 20 growth retarded fetuses at 26 to 36 weeks of gestation. Maternal venous blood was also collected and serum ferritin and cobalamin concentrations were measured by radio-immunoassay in the fetal and maternal samples. Results In the growth retarded group, the mean fetal serum concentration of cobalamin was higher than the normal mean for gestation (t = 3.27, P < 0.01), and this increase was significantly associated with fetal acidaemia (r = -0.686, P < 0.001) and erythroblastosis (r = 0.731, P < 0.001). In contrast, the fetal to maternal ferritin ratio was significantly reduced; there was a nonsignificant decrease in fetal serum and an increase in maternal serum ferritin concentration. There was an association between fetal serum ferritin concentration and erythrocyte count (r = -0.612, P < 0.01). Conclusions In placental insufficiency, as in postnatal starvation and Kwashiorkor syndrome, uptake and storage of cobalamin by the fetal liver may be impaired. The decrease in fetal to maternal ratio of ferritin could be the consequence of impaired placental perfusion.