Obstetric ultrasonographic findings and fetal chromosomal abnormalities: refining the association

In an attempt to refine the role of ultrasonography in screening and identifying fetuses at risk for chromosomal abnormalities, a retrospective review of patients undergoing genetic amniocentesis was undertaken.

Computer databases from the perinatal biology laboratory and cytogenetics laboratory of our institution were correlated to compare the results of the fetus' ultrasonographic examination with the cytogenetic results from amniocentesis. Univariate and multivariate analysis were used to determine the best correlations between ultrasonographic findings and chromosomal abnormalities (study 1). The results were used to construct regression analysis formulas and a Neural Network program to predict the presence or absence of chromosomal abnormalities in a second set of patients (study 2) undergoing genetic amniocentesis.

One hundred twenty-five chromosomal abnormalities were found in 3775 fetuses in study 1 (3.3%). Multivariate analysis showed significant correlations between anomalies of the central nervous system, heart, face and neck, and extremities and increased nuchal fold, increased bowel echogenicity, abnormal biparietal diameter-to-femur ratio, and the presence of chromosomal abnormalities. Regression equations and a Neural Network program successfully predicted the presence or absence of fetal chromosomal abnormalities in a second set of 901 at-risk fetuses.

A normal ultrasonographic examination result in patients who are at increased risk for fetal chromosomal abnormalities reduces the risk 2- to 3-fold, whereas the presence of any major ultrasonographic abnormality or certain minor abnormalities significantly increases the risk. The application of these results to low-risk patients is still premature.