[Prenatal diagnosis of hemoglobinopathies].

Fetal red blood cells are necessary for the antenatal diagnosis of hemoglobinopathies. Fetal blood may be obtained in utero, by amniocentesis or fetoscopy, from the 17th to the 20th week of pregnancy. At this time, biochemical techniques may detect bêta-thalassemia major (fetal synthesis of hemoglobin btaA chain totally absent or less than 2% and sickle cell disease (fetal synthesis of btaS chain, without any production of bêtaA chain). When fetal blood has been severely contaminated by maternal blood, purification techniques allow enrichment of the sample in fetal red blood cells by the elimination of adult reticulocytes which may lead to errors in diagnosis.