Ultrasound markers of chromosome aberrations on routine second trimester screening

Second trimester ultrasound examination for risk assessment of chromosomal abnormalities remains an important component of prenatal evaluation. We have conducted a retrospective study to evaluate the efficiency of ultrasonographic screening for the markers of chromosomal aberrations and to classify ultrasonographic markers according to the aberration they were found with. Over a 10 year period we performed 620 karyotype analyses of fetal blood taken by cordocentesis after detection of fetal anomalies in a second trimester scan in unselected population and 216 samples of peripheral blood of neonates having phenotypic features suspected for chromosomopathies. Ultrasound examination and cytogenetic data were obtained from the laboratory database. Chromosomal abnormalities were found in 36 (5,8%) fetuses with anomalies. Most frequently chromosomal aberrations were detected in fetuses with multiple anomalies (13,3%), heart anomalies (11,5%), short femurs (12,5%) and polyhydramnios (7,7%). The success rate of sonographic examination in detection of Down syndrome was 85%, and in detection of sex chromosome trisomies 80%. Trisomy 18, trisomy 13 and polyploidy were found prenatally in 100% each. Nearly 42% of trisomy 21 fetuses had heart anomaly, 35,3% polyhydramnios and 17,7% short femurs. Trisomy 18 fetuses had polyhydramnios in 87,5%, CNS anomalies in 62,5% and symmetrical IUGR in 50% of cases. All of the fetuses with monosomy X had short femurs. Ultrasonographic evaluation is the most sensitive screening method for the identification of fetuses having a high risk rate for chromosomal abnormalities in a low risk population.