Objective: To assess the value of fetal chromosomal abnormality screening by a maternal serum test plus fetal nasal bone length in second trimester (parallel test).
Methods: From January 2009 to December 2010, fetal nasal bone was measured at 19 - 22 weeks gestation in 6173 unselected cases. Karyotyping was performed in cases with a high risk for maternal serum test and/or abnormal fetal nasal bone length. All cases were followed-up postnatally.
Results: Nasal bone was assessed successfully in 5607 cases (90.83%). Normally it is increases with gestational age. The detection rate of chromosomal abnormality was 69.64% by maternal serum test, 79.76% by maternal serum test plus hypoplastic nasal bone and 83.93% by maternal serum test plus shortened nasal bone.
Conclusion: Fetal nasal bone hypoplasia is closely correlated with chromosomal abnormality. And sonographic evaluation of nasal bone may be a useful tool for screening chromosomal abnormality. The combination of maternal serum test and fetal nasal bone length will boost the detection rate of chromosomal abnormality.