European experience with prenatal diagnosis of congenital disease: a survey of 6121 cases.

The results of 6121 prenatal diagnoses established by 46 centers in eight West-European countries are reported. The percentage of "spontaneous" abortions following early amniocentesis (1.4%) does not seem to exceed the normal rate of spontaneous abortion in this period of pregnancy. A total of nearly 300 affected fetuses was detected, and in all but 5 instances the parents asked for interruption of the pregnancy. The majority of prenatal monitoring (75%) was carried out because of an increased risk of chromosomal aberration. In the group with higher maternal age 2.8% of the fetuses were affected; this figure was 4.6% for mothers older than 38 years. Monitoring because of an earlier child with trisomy 21 showed 1.3% fetuses with a chromosomal aberration, and 1.7% abnormal karyotypes were detected in the group where amniocentesis was performed for "miscellaneous reasons." In pregnancies where a parental translocation has been demonstrated, 6.7% of the fetuses showed an unbalanced karyotype and 25% were balanced carriers. Also discussed are results and organizatioal problems of prenatal monitoring for inherited metabolic disorders (206 analyses for 23 different enzyme defects) and for neural tube defects (about 2700 cases).