Nomogram of nasal bone length at 11-14 week of gestation in Indian women and their follow up till delivery

Background: The measurement of nasal bone length (NBL) according to gestational age and setting nomogram helps to ascertain NB hypoplasia. This can be used for early detection of trisomy 21 and other chromosomal abnormalities in low risk population. The objective of the study was to obtain nomogram of fetal nasal bone length at 11-14 weeks gestation with known prognosis pregnancies. Methods: A single centre, prospective crosses sectional study. Nasal bone length of 323 choromosomal and structural normal fetuses at 11-14 weeks gestation were measured by transabdominal ultrasonography, prospectively. The correlation between nasal bone and other biometric parameters was assessed by regression analysis and average±SD of nasal bone lengths were measured. Results: Fetal NB length (NBL) was visualized and measured in 281 patients (94.29%). Mean NB length was 3.07 mm, ranged between 1.60 mm to 4.6 mm and SD was 0.534. A linear growth pattern was observed between nasal bone and fetal biometric parameters. The significant correlation were found between the nasal bone and biparietal diameter (BPD) [NBL= 2.184+0.046 x BPD (r= 0.286, p value 0.000)], femoral length (FL) [NBL= 2.234+0.095xFL (r= 0.369, p value 0.000)] and crown-rump length (CRL) [NBL= 2.205+0.014 x CRL (r= 0.291, p value 0.000)]. Prenasal thickness (PT) increased linearly with CRL and POG. [PT= 1.081+0.006 x CRL (r= 0.16, p value= 0.02) and PT= 0.430+0.08 x POG (r= 0.15, p value= 0.028)]. Conclusions: Measurement of the nasal bone length at 11-14 weeks of gestation shows a linear growth pattern according to other biometric parameters of fetuses. Nomogram of nasal bone length was performed for early detection of trisomy 21 and other chromosomal abnormalities at low risk population.