Impact of first-trimester chromosome, DNA, and metabolic studies on pregnancies at high genetic risk: experience with 1,000 cases.

We describe the results and follow-up of chorionic villus studies in 1,034 pregnancies at risk for chromosome or metabolic disorders. Direct chromosome studies were successful in 99.7% and yielded results within a few days. Fifty pregnancies at risk for an unbalanced translocation, inherited from parents with many small reciprocal translocations, were a good test for the quality of the direct method. The 101 metabolic studies involving 28 disorders were correct in 99 pregnancies in the first trimester. In two cases a correct diagnosis was obtained by the confirmatory amniocentesis. DNA studies were carried out in pregnancies of male fetuses at risk for Duchenne muscular dystrophy and a few metabolic disorders. The abortion rate after chorionic villus sampling was 5.1% but more than half of the pregnant women were greater than or equal to 36 years old and have a spontaneous abortion rate of 10% between the 10th and 14th week according to Gustavii [Lancet 1:562, 1984]. Follow-up studies confirmed results of all chromosome studies after termination when there was fetal cell growth; the outcome of 504 consecutive continuing pregnancies showed no discrepancies of the phenotype after birth. It was concluded that first-trimester chorionic villi studies gave reliable results and were increasingly preferred by the patients, while the sampling can be considered a safe procedure based on the currently available data.