Prenatal diagnosis of genetic diseases: a study of 628 cases

Antenatal diagnosis was made in 628 pregnant women at risk to have infants affected by various genetic diseases. Prior to amniocentesis, extensive genetic counselling by a team composed of a geneticist, obstetrician, nurse and social worker was given and patients were usually not accepted for amniocentesis if they were not willing to interrupt the pregnancy based on abnormal cytogenetic and biochemical findings. The following criteria were agreed upon for accepting candidates for antenatal diagnosis: advanced maternal age, 37 years or older; previous chromosomally abnormal child; balanced translocation in the pregnant woman or her husband; previous child or sibling with a severe, sex linked, recessive disorder; both parents carriers for an autosomal recessive metabolic disorder like Tay Sachs disease, now amenable to antenatal diagnosis; previous child with open spina bifida or other severe neural tube defects. Of the 521 fetuses studied for cytogenetic indications there were 16(3.1%) with abnormal karyotypes (8 cases with trisomy 21; 2 cases with trisomy 18; 2 cases with trisomy 13; 2 cases with 47,XXX karyotype; one case with 47,XXY and one case with 45,D karyotype). 6 out of 18 fetuses were found to be male when sex determination was done because the mother was carrier of an X linked disease. Of 65 pregnancies monitored for Tay Sachs disease 17 fetuses (26.1%) were affected and selectively aborted. A follow up study of the pregnancies, the fetuses and the parental reaction to the counselling and amniocentesis was also carried out.