First trimester fetal diagnosis of genetic disorders: clinical evaluation of 250 cases.

Chromosome and enzyme determinations were performed in 250 pregnancies between the 7th and the 12th week of gestation. The majority of the tests were performed for risk of chromosomal abnormalities and 75% of the women were 35 years old or more. We describe a chorionic villi sampling (CVS) technique which proved to be highly efficient, with a diagnostic success rate of 97.7%. In the light of our experience we suggest that CVS is best performed between the 9th and 10th weeks of pregnancy. The average weight of the aspirated specimen was 20 mg with a lower limit of 5 mg which proved sufficient for diagnostic purposes. No major maternal complications were encountered and the slight bleeding observed in 14% of the cases during the days following the CVS should be considered a harmless effect of the aspiration technique. The proportion of fetal losses may lie between 4 and 7%. Paediatric monitoring of the 93 infants born so far and ultrasound examination of the pregnancies still in progress at the time of writing did not reveal any negative effect of CVS. Fetal-maternal transfusion and intrauterine infection are problems which need further basic investigations.