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Sonographic findings associated with fetal aneuploidy

Beryl R Benacerraf, MD
Section Editors
Louise Wilkins-Haug, MD, PhD
Deborah Levine, MD
Deputy Editor
Vanessa A Barss, MD, FACOG


There are two types of fetal chromosomal abnormalities identifiable by karyotype and microarray:

Aneuploidy, which is an abnormal number of chromosomes

Aberrations of chromosome structure, such as deletions, rings, translocations, and duplications

Aneuploidy is the most common genetic abnormality detected by prenatal diagnosis. Of the 6006 fetal karyotypes obtained at one center, 151 of the 207 abnormalities (73 percent) were aneuploidies (trisomy, triploidy, monosomy), and about 90 percent of these involved chromosomes 21, 18, 13, X, or Y (135/207 or 65 percent of all karyotypic abnormalities) [1]. Fetal chromosomal abnormalities are more common in the first and second trimesters than in live born infants, due to the high rate of spontaneous loss of these fetuses over the course of pregnancy [2,3]. Termination of affected pregnancies also plays a role.

The antepartum detection of fetal aneuploidy is one of the major goals of prenatal screening programs. Sonographic examination is useful because fetuses with abnormal karyotypes often have anatomic changes or anomalies. Sonographic findings, maternal serum analyte markers, and parental risk factors for genetic disease are all considered in determining the risk that the fetus is affected. However, invasive testing (amniocentesis or chorionic villus biopsy) is required to obtain a definitive karyotypic diagnosis.

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Literature review current through: Nov 2017. | This topic last updated: Mar 27, 2017.
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