Objective: To determine the association between fetal nasal bone hypoplasia and chromosomal aneuploidy at the mid-trimester ultrasound scans in high-risk pregnancy and to investigate its value of the nasal bone hypoplasia in second-trimester ultrasound screening of chromosomal aneuploidy.
Methods: The prospective study to measure the length of nasal bone was conducted from June 2003 to June 2005. The study population included 220 singleton pregnancies undergoing the genetic amniocentesis at 15 - 21 week’s gestation. Nasal bone hypoplasia was defined as nasal bone less than 2.5th percentile for the gestational age using the chart by Sonek et al.
Results: The nasal bone length showed to a linear correlation with advanced gestation (R2=0.194, p<0.000). Thirteen had an aneuploidy (5 trisomy18, 3 trisomy21, 3 inversions, 1 translocation and 1 duplication). The nasal bone was either absent or hypoplastic in 4/13 (30.7%) aneuploidy fetuses (2trisomy18, 2 trisomy21). Statistical difference was found between chromosomally normal and abnormal fetuses in the incidences of the nasal bone hypoplasia (p=0.01).
Conclusion: The nasal bone hypoplasia is associated with fetal chromosomal abnormalities in high risk pregnancy. But large studies are needed in general populations to determine the role of nasal bone hypoplasia either as an isolated marker or in combination with other sonographic marker for screening of chromosomal aneuploidy