CYTOGENETIC STUDIES IN FETAL BLOOD

In order to assess the effectiveness and reliability of cytogenetic di agnosis provided by fetal blood, we report the first 186 cases of feta l blood sampling performed for rapid karyotype between 19-37 weeks of pregnancy in our Prenatal Diagnosis Unit. The overall diagnostic succe ss rate was 98%, achieving 100% in the last period of the study. Chrom osomal anomalies were detected in 16% (29/182) of the fetuses. In malf ormed fetuses this rate increased from 8-9% in isolated malformation o r markers of aneuploidy to 50% in multiple malformations. In pregnanci es in which a previous cytogenetic study in amniotic fluid was inconcl usive, fetal blood made it possible to obtain a definitive result, wit h no discrepancies found at phenotypic follow-up examination. Interest ingly enough, one of the four previously defined as pseudomosaicisms w as found to be a non-mosaic in fetal blood, and only 1 of 4 mosaicisms was confirmed in fetal blood. In conclusion, cytogenetic analysis of fetal blood samples appears to be effective, rapid and reliable to est ablish the fetal karyotype in selected cases.