PRENATAL GENETIC DIAGNOSIS IN 3000 AMNIOCENTESES

We analyzed 3000 consecutive amniocenteses for prenatal diagnosis to assess the frequency of abnormalities, safety of the procedure, technical and interpretive difficulties and overall diagnostic accuracy. Chromosomal abnormalities were detected in 2.4 per cent of the 2404 pregnancies tested because of advanced maternal age (≥35 years), in 1.2 per cent of 240 monitored because of prior trisomy 21 and in 9.1 per cent of 55 examined for other cytogenetic indications. Mosaicism was detected in 0.4 per cent, and unexpected translocations in 0.4 per cent. Amniotic fluid was obtained on the first attempt in 99.3 per cent of the last 1000 cases, and cultures established from 99.7 per cent of patients attending our clinic. The fluid was discolored in 1.2 per cent of patients, a quarter of whom had missed abortions. The rate of spontaneous abortion after amniocentesis was 1.5 per cent. There were 14 diagnostic errors, six serious enough to affect the outcome of pregnancy. The karyotyping error rate was 0.07 per cent. We conclude that prenatal diagnosis is safe, highly reliable and extremely accurate. (N Engl J Med 300:157–163, 1979) THE last decade has witnessed a definite advance and new departure in medical genetics: prenatal diagnosis of genetic defects to determine whether a fetus believed to be at risk for some genetic disease actually has that disorder. Previously, genetic counseling was restricted to the passive role of providing prospective parents with risk figures for future offspring. Now, with the information provided by prenatal diagnosis, parents can decide whether or not they wish to continue the pregnancy. Many families previously unwilling to chance reproduction because of serious genetic risks can now bear children without fearing the birth of a child with. © 1979, Massachusetts Medical Society. All rights reserved.