Thickened nuchal fold in fetuses not at risk for aneuploidy.
Many studies have shown that a thickened nuchal fold in a second-trimester fetus is a sonographic sign suggestive of a high risk for Down syndrome. These series have included fetuses already at risk for aneuploidy because of advanced maternal age or abnormal maternal serum alpha-fetoprotein (AFP) levels. The authors describe the sonographic and karyotypic findings in 42 women younger than age 35 years whose fetuses were noted to have a thickened nuchal fold. Forty fetuses were not at risk for Down syndrome. Fourteen of the 42 fetuses (33%) had abnormal karyotypes; 11 had Down syndrome and one each had XXX, XO, and XYY. If the five cases with low maternal serum AFP levels are excluded, nine of the 37 fetuses (24%) with thickened nuchal folds had abnormal karyotypes. Amniocentesis would have been performed in one of those nine fetuses because of hydrocephalus. Thus, eight of 36 fetuses (22%) with thickened nuchal folds and no other indications for amniocentesis had abnormal karyotypes. When a thickened nuchal fold is present, the yield of abnormal karyotype is high (22%), making it possible to identify patients who would benefit from cytogenetic evaluation but who would not otherwise be candidates.
Benacerraf
B R
BR
Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
Laboda
L A
LA
Frigoletto
F D
FD
D000328:Adult; D000782:Aneuploidy; D003582:Cytogenetics; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007621:Karyotyping; D008423:Maternal Age; D009333:Neck / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal