RESUMO
Objective To evaluate the clinical significance of fetal nasal bone absence and thickened nuchal translucency ( NT) at 11-13 +6 weeks ultrasound screening .Methods A total of 4200 pregnant women with single fetus registered at Mother and Children ’ s Health Care Center in our hospital were examined at 11-13 +6 gestational weeks .Both fetal nasal bone and NT ultrasound evaluation were offered to assess whether nasal bone is absent and NT is thickened (>3.0 mm) in these cases.Particular attention was paid to the relationship between abnormal findings ,karyotype and pregnancy outcome .Results In all, 3492/4200 cases were included in the study with both NT measurement and nasal bone evaluation .Seven hundred and night cases were excluded because of unavailable clinical outcome .Among 3492 fetuses:(1) There were 3 cases absent of nasal bone .Among the 3 cases without nasal bone , 2 cases ( 1 case combined with thickened NT ) were trisomy 21(66.7%,2/3).(2) There were 351 cases with NT>3.0 mm (10.1%,351/3492).Among the 351 cases with thickened NT,there were 4 with trisomy 21 syndromes (1.14%,4/351,1 case combined with nasal bone absence ),1 with trisomy 18 syndrome,1 with Turner syndrome,6 with structural anomalies but normal karyotype (1.71%,6/351).(3)Among the 3139 cases with normal nasal bone and NT ,there were 8 cases with chromosomal or structural anomalies .Conclusions Absent nasal bone and thickened NT are important markers of trisomy 21 in the first trimester ultrasound screening .Thickened NT has significant correlation with other fetal chromosomal and structural anomalies .