Pattern of maternal F-cell production during pregnancy.

Maternal haemoglobin F production has been monitored in 11 normal pregnancies, with an immunofluorescent technique. In all cases there was a significant increase in the number of F-cells which reached a peak at 18-22 weeks' gestation. Comparison of the numbers of F-cells with the percentage haemoglobin F determined chemically indicated that the increase in maternal haemoglobin F synthesis results from an increased production of F-cells rather than from an increased synthesis of haemoglobin F by the F-cells. There was a highly significant increase in the number of F-cells in a pregnant beta-thalassaemia heterozygote.