First trimester examination of fetal nasal bone in the Turkish population.

AIM

The present study aims to assign the reference values for nasal bone length (NBL) screened at 11-14 weeks of pregnancy in the Turkish population, determining whether the NBLs specified for Caucasians can be validated for Turkish people.

MATERIALS & METHODS: The values of NBL were investigated in a total of 415 singleton fetuses that had Turkish parents and normal neonatal outcome. Sonographic measurements of NBL were done on a transabdominal midsagittal plane at 11-14 weeks' gestation. Regression analysis was used to assess the relationship between NBL and crown-rump length (CRL). Reference values, including the 5(th), 50(th) and 95(th)percentiles, were calculated for each gestational age.

RESULTS

The mean NBL was estimated to be 2.5 mm for 11-11 + 6/7 weeks, 2.9 mm for 12-12 + 6/7 and 3.4 mm for 13-13 + 6/7 weeks' gestation. The measurements of NBL showed a significant increase with CRL so that a linear and direct correlation was found between NBL and CRL (NBL = 0.267 + 0.043 x CRL, P < 0.001). Moreover, a significant and linear relationship was detected between NBL and gestational age (NBL = -3.858 + 0.537 x gestational age, P < 0.001).

CONCLUSION

The measurement of NBL is found to be achievable in the majority of first trimester pregnancies. The reference range of NBL in normal Turkish fetuses is established so that basic data can be recorded for further studies related to NBL measurements in screening for various chromosomal abnormalities including Down syndrome within Turkish population.