To define the value of Tei index of normal fetuses and to estimate the influence of gestational week and heart rate on the index. Fetal echocardiograms were performed on 225 normal single fetuses, which were divided into three groups (18 approximately 27(+6), 28 approximately 36(+6), 37 approximately 42 gestational weeks). The Tei indexes of both left and right ventricles (LV and RV) were measured by color Doppler ultrasonography. t test was used to compare the Tei index between LV and RV. The correlation between Tei index, gestational week and fetal heart rate were analyzed. The Tei indexes in three different gestational week groups (18 approximately 27(+6), 28 approximately 36(+6), 37 approximately 42 gestational weeks) were 0.37 +/- 0.08, 0.27 +/- 0.05, 0.22 +/- 0.05 of LV and 0.39 +/- 0.04, 0.30 +/- 0.05, 0.24 +/- 0.04 of RV respectively. There was significant difference of Tei index of RV and LV during 28 approximately 36(+6) gestational weeks (P < 0.05). The Tei index of LV and RV decreased linearly with advancing gestational week during 18 - 42 weeks (LV: r = -0.755, PP < 0.05; RV: r = -0.721, P < 0.05) in normal single fetuses. None of the fetal Tei indexes of LV and RV was related to fetal heart rate (LV: r = 0.133, P > 0.05; RV: r = 0.100, P > 0.05). Tei index may be useful, convenient and reliable in fetal cardiac function assessment.