Nuchal fold thickness at 14-16 weeks' gestation as measured by transvaginal sonography.

OBJECTIVE: To establish normal values of fetal nuchal fold thick-ness at 14-16 weeks of gestation by transvaginal sonography. METHODS: Transvaginal sonography was used to measure nuchal fold thickness in 182 normal pregnancies at 14-16 weeks of gestation. Nuchal fold thickness was measured as the distance from the outer skull bone to the outer skin surface in the transverse axial image in the suboccipital-bregmatic plane of the head. RESULTS: There was no significant association between nuchal fold thickness and gestational age (r = 0.084; P = 0.258). The mean (standard deviation) was 2.2 (0.5) mm and the 95th centile was 3.0 mm. CONCLUSIONS: The 95th centile of nuchal fold thickness measured by transvaginal sonography at 14-16 weeks is 3.0 mm.