Normal ranges of fetal nasal bone length during the second trimester in an Iranian population

Abstract

Objective: To provide a normal reference range for nasal bone length (NBL) during the second trimester of pregnancy in an Iranian population.

Methods: This cross-sectional study was performed on 3201 fetuses at 15 to 28 weeks of gestational age (GA). Both singleton and twin fetuses were evaluated. The relationship between NBL and GA was determined and percentile values for each gestational week were provided.

Results: NBL measurement was obtained in 98% of singleton and 96% of twin fetuses. There was a linear relationship between GA and NBL both in singleton (R(2) = 0.62) and in twin (R(2) = 0.74) fetuses. There was no significant difference between twins regarding NBL (p = 0.18).

Conclusion: We have provided the normal reference range for NBL during the second trimester in an Iranian population. NBL in singleton and twin fetuses is similar and there is no significant difference between twins regarding NBL.