To determine the reference ranges and Z-score equations for aortic and pulmonary diameters in normal fetuses based on the measurements of biparietal diameter (BPD), femur length (FL), or gestational age (GA) using fetal echocardiography at 11~17 weeks of gestation.

A total of 245 singleton normal fetuses were enrolled at 11~17 weeks of gestation. Non-cardiac fetal biometric parameters including BPD, FL, and GA were recorded. Fetal cardiac measurements of aortic (AO) and pulmonary valve annulus diameters (PA) at end-systole were performed. The normal reference ranges and Z-score equations of AO and PA at 11~17 weeks of gestation were established. Using GA, BPD, and FL as independent variables, and AO and PA as dependent variables, Z-score equations of normal fetal AO and PA were established.

The relationship of AO and PA with non-cardiac biological characteristic parameters (GA, BPD, and FL) can be well described by using a simple linear regression model. AO and PA had a significant linear correlation with GA, BPD, and FL; among them, the correlation with BPD was the most significant.

The AO and PA of normal fetuses at 11~17 weeks of gestation increase with gestational age. The normal reference ranges and Z-score equations of AO and PA at 11~17 weeks of gestation have been preliminarily established, thus providing accurate reference criteria for the early assessment of fetal cardiovascular growth by fetal echocardiography, which has potential value in early screening of fetal congenital cardiac malformation.