Detection of chromosomal abnormalities, an outcome of ultrasound screening. The Eurofetus Team.

Chromosomal abnormalities were recorded from all the fetuses of women who benefited from sonographic examinations in the Eurofetus centers, excluding those for whom karyotyping was motivated by age or personal history. Among the 378 chromosomal abnormalities recorded, 210 were detected before birth (sensitivity = 55.6%). Down syndrome (trisomy 21) represented 197 cases, or which 68 were detected before birth (sensitivity = 34.5%). Eighty-two of the cases of Down syndrome had associated structural abnormalities; the sensitivity in these cases increased to 57%. Among the 115 cases of Down syndrome without structural abnormalities, 21 (18.3%) had associated abnormal ultrasound findings that led to prenatal detection. Sensitivity of prenatal detection was 58.1% for trisomy 13 and 79% for trisomy 18. For the abnormalities detected before birth, spontaneous fetal death occurred in 27% of cases, and an early termination of pregnancy was decided in 53% of cases.