Obstetric aspects of midtrimester fetal blood sampling by needling or fetoscopy.

We describe our experience at University College Hospital, London, with the first 135 patients submitted to midtrimester fetal blood sampling for antenatal diagnosis of beta-thalassaemia major, other thalassaemias and homozygous sickle cell disease. Blind needling and fetoscopy with sampling are evaluated and their application discussed. With experienced operators 9 per cent of patients experienced a fetal loss.