Down syndrome (DS) is the most common chromosomal aneuploidy to result in a live birth. Absent nasal bone has been consistently observed in fetuses with ds. Multiple studies have been conducted to measure and compare the nasal bone length (NBL) in different races and ethnicity and is found to vary in size. In countries, such as India where often only the second trimester scan is performed for screening of aneuploidies, NBL could be regarded as a useful marker.

To estimate the NBL of fetuses at 18 to 22 + 6 weeks gestational age in an Indian population, establish a normogram and compare it with that of the Caucasian population.

Prospective observational study in a tertiary care hospital with 500 antenatal subjects after considering the inclusion and exclusion criteria.

The normogram was established and found to be comparable to previously established ones for Indian subjects. The 5th centiles for 18-18.6, 19-19.6, 20-20.6, 21-21.6 and 22- 22.6 weeks of gestations were 3.4, 3. 5, 4.2, 4.3 and 5.4 mm respectively. The NBL increased with gestational age (GA), and the mean NBL was 5.48 mm. No correlation was noted with maternal age, sex of fetus or religion. The NBLs were significantly shorter than those of the Caucasian population.

Mean NBL values of Indian population are less than the mean NBL of Caucasian population. This along with the GA needs to be considered in counseling patients and decisions regarding further invasive and noninvasive tests.

Vikraman SK, Chandra V, Balakrishanan B, Gudi A, Batra M, Kannoli G. Nasal Bone Length Normogram of Mid-second Trimester Euploid Fetuses of an Indian Population. Int J Infertil Fetal Med 2015;6(1):25-29.