Purpose of investigation: To develop a nomogram for estimating nasal bone length (NBL) at 11(+0) - 13(+6) weeks of gestation in 554 consecutive cases and to determine the value of NBL measurement in screening for chromosomal abnormalities.
Materials and methods: NBL and crown-rump length (CRL) were examined in 554 fetuses at 11(+0) - 13(+6) weeks' gestation. A nomogram for NBL was developed with data from 479 healthy fetuses in which fetal profile examination was possible. Reference values, including percentiles, weie calculated for each gestational age.
Result: A linear correlation was noted between CRL and NBL in healthy fetuses at 11(+0) - 11(+6), 12(+0) - 12(+6) and 13(+0) - 13(+6) weeks of gestation. Mean NBL was 2.18 +/- 0.53 mm, 2.46 +/- 0.45 mm, and 2.91 +/- 0.55 mm in healthy fetuses, for these time frames, respectively. NBL increased significantly with CRL from respective means of 2.26 +/- 0.43, 2.60 +/- 0.48, 2.77 +/- 0.43, and 3.16 +/- 0.52 mm at 45 - 54.9, 55 - 64.9, 65 +/- 74.9, and 75 - 84 mm.
Conclusion: The authors developed a NBL nomogram with data from normal, healthy Turkish fetuses at 11(+0) - 13(+6) weeks of gestation. These reference ranges may prove useful in prenatal screening and diagnosis of syndromes known to be associated with nasal hypoplasia.