[Prenatal diagnosis of a male fetal carrier of fragile X chromosome by the amniotic fluid cells].

A prenatal diagnosis of fragile X fra(X)(q28) has been performed in a pregnant woman obligate carrier of fra(X) by analysis of amniotic fluid cells taken by amniocentesis. The fra(X) has been observed in 30% (8/26) of the metaphases of the male fetus. These results were obtained within 10 days after amniocentesis using the in situ technique on cells grown first in Ham Medium supplemented with newborn calf serum and a serum substitute and changed for the last 19 hours with Tc 199 medium with 5% newborn calf serum and methotrexate (10 mg/l). This technique showed that fra(X) is not a clonal phenomenon and that its expression is related to the cell types and the origin of the studied cells.