ABSTRACT
Objective To establish the reference ranges for fetal cardiac axis in the mid-second trimester and to evaluate the use of fetal cardiac axis in prenatal diagnosis.Methods 6744 unselected singleton pregnancies were enrolled from September 2008 to October 2010.Routine screening scan of second trimester and fetal echocardiography were performed at 18- 23+6 weeks gestation.Fetal cardiac axis was measured on the four-chamber view of the heart.Results The 6744 fetuses had a mean cardiac axis of (37.03 ± 6.10)°,ranging from 9.80° to 102.41°. Using above or below 95％ range of population (26.63° -49.40°) as a cut-off,there were significant difference of cardiac axis between normal group [(36.96 ± 5.91)°,P ＜0.01] and the group with heart defects [(43.12 ± 15.67)°,P ＜0.01],the group with intrathoricic anomalies or abdominal wall defect [(51.74 ± 15.97)°].ConclusionsThe reference ranges of fetal cardiac axis for local population in mid-second trimester may helpful for detecting congenital defects.Presence of an abnormal cardiac axis in the fetuses is associated with a substantial risk of congenital heart disease and/or other extra cardiac defects.