Feasibility of placental biopsy in the second trimester for fetal diagnosis.

Second-trimester prenatal diagnosis by placental biopsy was possible in 200 of 220 patients (90.9%) to whom it was offered to expedite cytogenetic analysis. Cytogenetic analysis was successful in 190 cases (95%) when the material obtained was greater than 2 mg. We found five chromosome abnormalities; 47,XX, +21 (two cases); 47,XY, +18 (one case); and 45,XX,t (D;G) (two cases). There was one abortion 4 weeks after the placental biopsy (0.4%). If further experience confirms the accuracy, safety, and reliability of this method beyond the first trimester, it can be offered to mothers to expedite the cytogenetic, biochemical, and deoxyribonucleic acid analysis.