Hemoglobinopathies affecting maternal-fetal oxygen gradient during pregnancy: molecular, biochemical and clinical studies.

The higher oxygen (O2) affinity of fetal blood compared to maternal blood has been considered advantageous for the survival of the fetus. However, there is little information on infants born to mothers who carry a hemoglobin (Hb) variant with altered O2 affinity. This report describes two mothers and their newborn infants, each with a different globin chain variant are identified as Hb Linköping, [beta36(C2)Pro-->Thr] and Hb Sunshine Seth [alpha94(G1)Asp-->His]. Hb Linkoping is a known high O2 affinity variant, while Hb Sunshine Seth was found to have a low affinity for O2. One mother and her newborn, both with a heterozygosity for Hb Linköping, had P50 values of 1.9 and 2.5 kPa, respectively, a reversal of the physiological maternal-infant gradient. The other mother and her newborn, who were heterozygous for Hb Sunshine Seth, had P50 values of 4.7 and 4.4 kPa, respectively, a minimal gradient. The Hb F, plasma erythropoietin, and 2,3-diphosphoglycerate (2,3-DPG) levels were normal in both infants. The newborns were clinically normal.