Abstract： Objective To analyze the feasibility of prenatal ultrasound quantitative measurement of the angles between trachea and bilateral bronchi as a new diagnostic tool for fetuses with heterotaxy syndrome.Methods The angles between trachea and bilateral bronchi were measured at 18-34+6 gestational weeks for 200 fetuses with normal ultrasound findings (normal group) and 41 fetuses with heterotaxy syndrome [35 right atrial isomerisms (right group) and six left atrial isomerisms (left group)] diagnosed by ultrasound and confirmed after abortion or induction (case group) in Chongqing Health Center for Women and Children from October 2015 to December 2018.Scatter plots of left/right bronchus angle (α / β) ratios were drawn.Differences in bilateral bronchus angles between the three groups were statistically analyzed using one-way analysis of variance and paired t-test.Results In the normal group,scatter plots showed the α/β ratios were relatively constant at 0.8-1.0 with larger β than α (t=-33.14,P＜0.05),indicating that the right bronchus always went more steeply than the left one.In the case group,the α/β ratios were around 1.0.In the right group,the α value increased and was close to the β value [(153.90±5.43) ° vs (156.02±5.59) °,t=-2.56,P＞0.05] and presented as bilateral right bronchial angle;in the left group,the β value decreased and was close to the α value [(147.38±3.16)° vs (148.82±5.56) °,t=-1.18,P＞0.05] and presented as bilateral left bronchial angle.There were significant differences in the α and β values among the normal group,the right and left groups (all P＜0.05),and the bronchial angles of the right group were both greater than those of the left group (all P＜0.05).Conclusions Prenatal ultrasound measurement of the angles between trachea and bilateral bronchi can be used as an indirect indicator for the diagnosis of heterotaxy syndrome.