NUCHAL TRANSLUCENCY IN THE 1ST TRIMESTER

All fetuses reported as having nuchal (nape of the neck) thickening or translucency detected by a first trimester ultrasound at 2 centres we re reviewed to determine the incidence of aneuploidy. Twenty nine preg nancies were registered, amongst which 12 (41%) had an abnormal karyot ype, the most common aneuploidy being trisomy 21 (5 fetuses). The like lihood of aneuploidy increased with increasing thickness of the transl ucency. Where the karyotype was found to be normal, there was complete resolution of this ultrasound appearance by the second trimester in 1 5 of the 16 ongoing pregnancies: 9 have delivered normal neonates and 6 pregnancies are continuing. The other fetus developed evidence of a skeletal dysplasia by the second trimester.