Ultrasonographic measurement of fetal nasal bone in the Korean population at the first and second trimester

Abstract

POPULATION AT THE FIRST AND SECOND TRIMESTER EUI JUNG, HYE-SUNG WON, JUNG-SUN KIM, JAE-YOON SHIM, PIL RYANG LEE, AHM KIM, Asan Medical Center, University of Ulsan, Obstetrics and Gynecology, Seoul, South Korea, Asan Medical Center, University of Ulsan, Pathology, Seoul, South Korea OBJECTIVE: To establish the reference range of fetal nasal bone length(NBL) at the 1st and 2nd trimester in the Korean population and to determine the accuracy of prenatal NBL by postmortem examination including radiographs and autopsy. STUDY DESIGN: A total of 404 consecutive ultrasound examinations were performed at 11-14 weeks of gestation for nuchal translucency and nasal bone measurement and 820 consecutive fetuses underwent ultrasound examination at 18-26 weeks of gestation in Asan Medical Center. And the association between chromosomal abnormality and nasal bone absence or hypoplasia(smaller than 2.5th percentile) was analysed. Twenty-two fetuses with congenital anomaly or intrauterine death had undergone sonographic measurement of NBL before termination of pregnancy and were examined by radiographs and autopsy following termination. RESULTS: At the 1st trimester, the visualization of fetal profile was obtained in 398 fetuses (98.5%), and linear regression was performed. The incidence of nasal bone absence was 3/398 (0.75%). One fetus had T.21, one with T.18 and the other was acrania with euploidy. At the 2nd trimester, fetal profile was successfully examined in 818 fetuses(99.8%) and the NBL increased linearly with gestation. During this period, 6 fetuses with chromosomal abnormality (including 2 T.21) were detected and only one fetus with T.21 had hypoplastic nasal bone. Hypoplastic nasal bones was seen in 14/812 (1.7%) chromosomally normal fetuses. NBL measured by ultrasound was similar to that confirmed by autopsy and longer than by postmortem radiograph. CONCLUSION: We present the normal range of NBL at the 1st and 2nd trimester and their linear relationship with CRL and gestational age. Although numerically limited, our experience shows that the NBL in the 2nd trimester in Korean seems to be shorter than that of Caucasian and similar to Chinese. So different normal ranges for different races are required, and relative percentile is SMFM Abstracts S181