Abstract: Objective To explore the relationship between fetal heart axis angle and the fetal congenital heart disease (CHD) in the second trimester of pregnancy by measuring the angle of fetal heart axis. Methods There were 52 fetuses in the abnormal group and 104 in the control normal group were selected as the research objects, all the pregnant women were taken maternal and infant health records and taken standardized prenatal ultrasound screening in Beijing Obstetrics and Gynecology Hospital, Capital Medical University from December 2017 to May 2019. According to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) practice guidelines for sonographic screening examination of fetal heart, the fetal axis angle was measured in the four-chamber view of the fetus. Results There was no significant difference in maternal age and fetal age between the abnormal group and the control group (t=1.825、-0.928,P>0.05). The cardiac axis angle of abnormal group was (50.03°±24.02°), and that of control group was (42.64°±6.30°) respectively. The difference was statistically significant between the two groups (P<0.05). The proportion of abnormal axis was 30.77% (16/52) in abnormal group and 0.96% (1/104) in control group, with statistical significance (P<0.05). The risk of CHD in fetuses with abnormal axis angle increased by nearly 45 times, it suggested that the n abnormal fetal heart axis angle is closely related to CHD. Conclusion Abnormal fetal cardiac axis is closely related to fetal CHD and has certain value in CHD diagnosis. If abnormal fetal cardiac axis was identified by ultrasound screening, more attention should be paid to fetal cardiac examination.al cardiac axis was identified by ultrasound screening, more attention should be paid to fetal cardiac examination.

Key words: fetal congenital heart defects, ultrasonography, fetal cardiac axis