Abstract： Objective To quantitatively study right ventricular function in the normal second and third trimester fetuses by M-mode tricuspid annular displacement(TAD).Methods TAD was measured using conventional M-mode echocardiography on 161 normal second and third trimester fetuses with gestation age (GA) between 19-38 weeks,meanwhile multiple parameters for evaluating right ventricular function were obtained using pulsed Doppler echocardiography (PW) and myocardial Dopple tissue imaging (DTI).The correlation between TAD and other parameters were analyzed using SPSS 17.0.Results In normal second and third trimester fetuses,the TAD was (9.38 ± 1.71)mm with a range of 5.79-13.90 mm,and was increased with the growth of GA.TAD was correlated with GA,E,A,Em,Am and Sm significantly (r =0.759,0.547,0.320,0.497,0.483 and 0.598 respectively,all P ＜0.001).TAD was not correlated with HR(P ＞0.05).TAD showed differences between the second trimester fetuses and the third trimester fetuses (P ＜ 0.05).Conclusions In normal second and third trimester fetuses,the TAD is increased with the growth of GA,and has good correlation with GA,E,A,Em,Am and Sm respectively,and may become a new promising modality to evaluate function of RV simply and accurately.The technique will be propitious to use in hospitals (without DTI) because of simplicity of operator and lower requirement on the technology and equipment precision.