Nasal bone length: the long and short of it. Evaluation of the reference values for the fetal nasal bone length at 16 to 25 weeks of gestational age in an Indian population.

OBJECTIVE: To establish a reference interval range for the fetal nasal bone length (NBL) in an Indian population. METHODS: A retrospective study of antenatal ultrasound records of fetuses at 16 to 25 weeks in singleton pregnancies. NBL, biparietal diameter (BPD) and femur length were noted in 6436 observations of singleton, euploid, nonmalformed pregnancies. RESULTS: The 50th centile for NBLs increased from 3.4 to 6.9 mm from 16th to 25th week of gestational age. The relation between nasal bone and gestational age, BPD and femur length were found and noted. The NBLs were found to be shorter when compared with other ethnicities. CONCLUSIONS: A reference range for fetal NBLs at 16 to 25 weeks in an Indian population and its relation with fetal biometry was established.