Nuchal Translucency Sign of Defects Other Than Trisomy 21

About half of chromosomally abnormal fetuses have defects other than trisomy 21

FRIDAY, Jan. 6 (HealthDay News) -- About half of fetuses with increased nuchal translucency and chromosomal defects have problems other than trisomy 21, according to a study in the January issue of Obstetrics & Gynecology. Other conditions, such as Turner syndrome and trisomy 18, are associated with a nuchal translucency size that differs from fetuses with trisomy 21.

Karl Oliver Kagan, M.D., of King's College Hospital Medical School in London, and colleagues searched a database and identified 11,315 pregnancies in which nuchal translucency was above the 95 centile for crown-rump length, including 2,168 (19.2%) with chromosomal abnormalities. The incidence of chromosomal defects increased with nuchal translucency thickness, the investigators found.

In most fetuses with trisomy 21, the researchers report that nuchal translucency thickness was less than 4.5 mm, compared to 4.5-8.4 mm in fetuses with trisomies 13 or 18, and 8.5 mm or more in those with Turner syndrome.

"In fetuses with increased nuchal translucency, approximately one half of the chromosomally abnormal group is affected by defects other than trisomy 21," the authors write. "The distribution of nuchal translucency is different for each type of chromosomal defect."

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