Fetal Nasal Bone Length in Euploid and Aneuploid Fetuses Between 11 and 20 Weeks' Gestation: A Prospective Study

To develop normative data for nasal bone length between 11 and 20 weeks' gestation and to assess the utility of nasal bone hypoplasia in the detection of fetal aneuploidy in the second trimester. Well-dated, nonanomalous fetuses were examined between 11 and 20.9 weeks' gestation. The nasal bone was assessed and measured, and normative data from 11 to 20 weeks' gestation were determined. The nasal bone lengths in fetuses with confirmed aneuploidy were compared with the normative data. The fetal nasal bone length increased linearly with advancing gestational age. Nomograms including the 10th, 50th, and 90th percentiles were created. Nasal bone hypoplasia was seen in 6 of 6 cases of fetal trisomy in the second trimester. Nasal bone hypoplasia in the early second trimester identifies a cohort of fetuses at high risk for aneuploidy.