Fetal diagnosis of hereditary diseases. WHO Working Group.

Fetal diagnosis, based on amniocentesis in the second trimester of pregnancy, in conjunction with selective termination of affected pregnancies, is currently one of the most important components in the control of hereditary disease. Extensive experience has been gained with its use in the last decade, and in the hands of experienced investigators it is a safe and reliable procedure. However, there are still significant limitations to its use. Many serious congenital abnormalities cannot be diagnosed because of difficulty in identifying pregnancies at risk. In addition, for mothers at high risk, mid-trimester diagnosis is associated with great anxiety.A method for earlier fetal diagnosis, based on sampling of chorionic villi at 8-10 weeks' gestation, is beginning to enter clinical practice. At present, the technique is still at the research stage, but it has great potential for increasing the acceptability of fetal diagnosis. There is evidence that cytogenetic, biochemical, and DNA analyses can be applied to chorionic villus material, but the ultimate usefulness of the procedure will depend on the associated obstetric risk, which has not, as yet, been clearly defined.