Objective: To establish the reference range of fetal NBL for Indian population and study the ethnic variation in fetal Nasal Bone Length.
Methods: Prospective Observational Cohort Study was conducted at a North Indian tertiary care Hospital in fetuses at 11-28 weeks. Fetal Nasal Bone Length was measured in mid-sagittal section of the face using electronic callipers. Gestational age was calculated based on Last Menstrual Period (LMP) or first trimester scan when LMP was not known. A total of 250 fetuses were scanned followed by post-natal follow up clinical examination to rule out aneuploidies.
Results: The NBL values showed positive linear correlation with gestational age. The median NBL values increased from 1.9 mm at 11-12 weeks till 8.0mm at 27-28 weeks. The NBLs in Indian fetuses were significantly shorter as compared to Western populations.
Conclusion: An indigenous reference range for fetal NBLs at 11-28 weeks better suited to be used in Indian population.