Abstract: Objective To explore the value of real-time biplane imaging technology to measure of cardiac cycleization in the middle and late pregnancy. Methods There were 716 subjects, all of whom were pregnant women in middle and late pregnancy with prenatal ultrasound received by Yanqi Hospital of the second Division of Xinjiang Production and Construction Corps at Januany 2019 to April 2021. 4. According to the gestational week, 456 pregnant women were divided into middle group and 260 cases in late group. Compare the two groups of conventional ultrasound indexes （FS、 LVEDV、 LVM、 CO、 SV、 LVEF、 LVESV）, Real-time biplane imaging measures （Vs、 Vd、 S、 SRd、 SRs）. To analyze the correlation between the change rule of cardiac cycle and gestational age of normal fetuses with conventional ultrasound and biplanar imaging, and real-time biplanar imaging characteristics. Results Comparing FS、 LVEDV、 LVM、 CO、 SV、 LVEF, and LVESV in the two groups, the late group was higher than the middle group （P<0.05）. Vs and Vd were higher in the late group than in the middle group （P<0.05）, and the difference between S、 SRd and SRs in the middle group was not significant （P>0.05）; the fetal strain rate curve consisted of a forward wave and a negative wave, and the overall strain curve showed a negative unipeak curve trend. In 716 fetuses, Pearson analysis showed a positive correlation between gestational age and peak diastolic velocity, peak systolic velocity, left ventricular myocardial weight, output per blog, short axis shortening, cardiac output, left ventricular end systolic volume, and left ventricular end diastolic volume in middle and late pregnant women （P<0.05）. Conclusion The real-time biplane imaging technology can accurately measure the normal fetal cardiac cycleization changes in the middle and late pregnancy, and can evaluate the local and overall function of the fetal myocardium at an early stage. It has good application values.

Key words: real-time biplane imaging, middle and late pregnant women, fetus, cardiac cycleization, ultrasound