Purpose: to estimate the performance of ultrasound to detect gestations at risk for fetal chromosomal abnormalities. Methods: four hundred and thirty-six patients selected for the study had undergone ultrasound examination and fetal karyotyping, between March 1993 and March 1998. Two hundred and seventy-seven patients had fetal karyotype for fetal malformation detected on ultrasound and 158 for parental anxiety with normal ultrasound examination. Ultrasound sensitivity and specificity were calculated using fetal karyotype as gold standard. The relative risk for each chromosomal abnormality was calculated according to the altered system on ultrasound examination and the risks of the presence of one or more abnormalities on ultrasound, using the Epi-Info 6.0 software package for statistical analysis. Results: the relative risks for chromosomal abnormalities were 89 for face malformations, 53 for abdominal wall and cardiovascular, 49.6 for neck, 44.6 for extremities, 42.4 for lung, 32.7 for gastrointestinal tract, 27.4 for central nervous system and 23.0 for urinary tract malformations. The relative risk for fetal chromosomal anomalies for genital, thorax, spine and muscle and/or skeletal malformations was not appropriate for calculation because they occurred at very low frequencies. An isolated malformation detected by ultrasound is associated with a 7.8 times higher relative risk for chromosomal anomalies than none, and associated morphologic malformations have a 33.8 times higher relative risk for chromosomal abnormalities. Conclusion: ultrasound has good performance to detect gestations at risk for chromosomal abnormalities.
Ultrasound; Fetal chromosomal abnormalities; Prenatal diagnosis; Karyotype; Fetal malformation
