Abstract
The authors aimed to establish the reference ranges of fetal nasal bone length (NBL)
in the second trimester and evaluate the relationship between fetal NBL and biparietal
diameter (BPD) at 17–22 weeks of gestation in the Indian population. The authors also
determined the normal ranges of the fetal nasofrontal angle (NFA). Ultrasound examination
was done in 486 singleton pregnancies at 17–22 weeks of gestation. The fetal NBL was
measured in millimeters in a strict sagittal view of the fetal head. The NFA was also
measured in this mid-sagittal profile. The authors present the normal range of fetal
NBL. Mean NBL was found to increase linearly with advancing gestation and BPD. The
NBL appears to be marginally longer in Indian fetuses than other Asian fetuses. The
minimum, maximum, and mean NFA values were 112, 142, and 130 degrees. The authors
present the normal range of NBL in the second trimester in the Indian population and
identify its linear relationship with gestational age. The normal range varies among
races and so a relative percentile is a more reliable screening criterion than an
absolute value. The authors present the normal ranges of fetal NFA from 18 to 21 weeks.
Keywords
Ultrasonography - Nasal bone - Fetus
