Objective ·To assess the value of ultrasonography in the diagnosis of fallopian tubal heterotopic pregnancy (THP). Methods ·From January 2010 to December 2022, among the 13 082 cases of ectopic pregnancy diagnosed and discharged from the International Peace Maternity ＆Child Health Hospital, Shanghai Jiao Tong University School of Medicine, 88 cases suspected of having THP were selected as the study objects. Pre-admission ultrasound images and clinic data from these cases were collected. Then these cases were divided into three groups according to their gestational age at the time of ultrasonography: Group Ⅰ, gestational age within 38 d; Group Ⅱ, gestational age of 39?45 d; Group Ⅲ, gestational age of 46?73 d. The incidence of THP, pregnancy outcomes, the sensitivity and specificity of ultrasound diagnostic results, and the consistency between postoperative pathological results, discharge diagnosis and preoperative ultrasound diagnosis results (i.e. accuracy) were retrospective analyzed. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic value of ultrasonography for THP in these three groups. Results ·In all the ectopic pregnancy cases, 72 THP cases were confirmed by postoperative pathology or further ultrasonography. The incidence rate of THP was 0.5% among the 13 082 patients with ectopic pregnancy. There were two types of preoperative ultrasound images of these 72 THP cases: Type Ⅰ, echogenic mass in gestational sac, accounting for 30.6%; Type Ⅱ, hypoechoic and mixed echogenic mass, accounting for 69.4%. In addition, 54.2% of TPH patients underwent salpingectomy, and the intrauterine live birth rate in TPH patients was 59.7%. There were significant differences between groups in the overall sensitivity (91.7%), specificity (81.3%), and accuracy (89.8%) of ultrasonography in the diagnosis of THP (all P<0.05). Sensitivity and specificity in Group Ⅰ were significantly lower than those in Group Ⅲ; the accuracy of Group Ⅰ was significantly lower than that of Group Ⅱ and Group Ⅲ (all P<0.05). ROC curve analysis further showed that the diagnostic value of ultrasonography for THP was low for cases within 38 d of pregnancy, whereas for cases with gestational ages of 39?45 d and 46?73 d, ultrasonography demonstrated notable diagnostic value. Conclusion ·Ultrasonography has high diagnostic value for THP. The gestational age at the time of ultrasonography is closely related to the sensitivity, specificity, and accuracy of diagnosing THP. Special attention should be paid to ultrasonography for pregnant women with a gestational age over 46 d to assist in the diagnosis of THP.