Obstetric outcome and problems of mid-trimester fetal blood sampling for antenatal diagnosis.

Detailed follow-up is presented of 335 pregnancies in which mid-trimester fetal blood sampling was performed for the diagnosis of a haemoglobinopathy, mostly beta-thalassemia. There were three twin pregnancies. Thirty-eight fetuses were lost including four in whom a diagnosis of thalassemia major was made. Placentacentesis was particularly associated with fetal vessel trauma, exsanguination and early intrauterine fetal death, while late complications associated with fetoscopy or failed fetoscopy necessitating subsequent placentacentesis included spontaneous abortion, leakage of amniotic fluid and premature onset of labour.