To establish the normal data of the fetal thorax, and to evaluate its values in the diagnosis of fetal thorax malformation.

Totally 398 normal singleton fetuses at 16 to 36 gestational weeks(GW) were enrolled, 2D-US and 3D-US VOCAL technique were used to measure the 2D data and 3D volumes on the transverse section at the level of the four-chamber view, and the correlation among all measurements with GW was analyzed. Thirty fetuses collected randomly were examined to analyze the reliability. Nine fetuses with congenital thoracic dysplasia (CTD) and 10 fetuses with congenital diaphragmatic hernia (CDH) were assessed and compared with the normal fetuses.

① In healthy controls, the fetal thoracic 2D measurements and 3D volumes increased along with the growth of the GW. The regression equations were listed as follows: thoracic transverse diameter (cm)=-0.002 GW²+ 0.301GW-1.510; thoracic anteroposterior diameter (cm)=0.003GW²+ 0.046GW+ 0.666; thoracic area (cm²)=0.071GW²-1.466 GW+ 14.728; thoracic circumference (cm) =0.01GW²+ 0.313GW+ 3.341; thoracic volume (cm³)=0.285GW²-7.797GW+ 66.592; lung volume (cm³)=0.178GW²-5.317GW+ 45.539; the ratio of lung volume to thoracic volume=0.005GW+ 0.396. ② The reliabilities of the data obtained by the same /two different operators were good. ③ CTD group was obviously lower than the healthy controls in all thoracic measurements (all P<0.01). There was no statistical difference in the 2D data between the CDH group and healthy controls (P>0.05), while the 3D volumes and the ratio of lung volume to thoracic volume were obviously lower than those in the healthy controls (P<0.01).

2D-US can evaluate the fetal thoracic development and malformation preliminarily, but 3D-US VOCAL technology plays an important role in distinguishing different types of thoracic malformations.

Ultrasonography, prenatal; Thoracic malformation