To explore the strategy for prenatal ultrasonic diagnosis of right heart system enlargement in fetuses by analyzing its ultrasonic characteristics and causes.

The data of 685 fetuses with enlarged right heart system diagnosed by fetal echocardiography from January 2013 to August 2017 at Shaanxi Province Centre for the Ultrasound Diagnosis of Fetal Congenital Heart Diseases were analyzed. The characteristics, causes, and type of enlarged right heart system were summarized.

Five hundred and fifteen fetuses had absolute enlargement, accounting for 75.18% (515/685) of all cases. There was simple enlargement of right heart system and secondary enlargement. The main reason for the secondary enlargement was the increase of the right heart system load caused by various lesions, including pre-load and post-load. One hundred and seventy (170/685, 24.82%) fetuses had relative enlargement of right heart system, because of small left heart system, including simple enlargement of left heart system, left ventricular dysplasia, and other abnormalities. The proportion of fetuses with enlarged right ventricular system in late pregnancy (gestational age≥28 weeks) was 70.42%, and the proportion of fetuses with small left ventricular system in late pregnancy (gestational age≥28 weeks) was 51.67%.

The enlargement of right heart system in fetuses is divided into absolute enlargement and relative enlargement, with the former being the predominant type. After excluding all clear lesions that may cause secondary enlargement of right heart system, simple enlargement with a good prognosis could be considered. The prognostic evaluation of fetal right ventricular system enlargement should be based on the specific situation of different structural changes.