Changes in fetal cardiac axis between 8 and 15 weeks' gestation.

Area of Science:

• Fetal Medicine
• Embryology
• Cardiology

Background:

• The embryonic cardiac axis undergoes significant changes during early pregnancy.
• Understanding normal development is crucial for identifying potential abnormalities.
• Previous studies have not fully detailed the axis changes in the late first and early second trimesters.

Purpose of the Study:

• To document the normal changes in the embryonic/fetal cardiac axis.
• To establish reference ranges for the cardiac axis between 8 and 15 weeks of gestation.
• To assess the potential of cardiac axis measurement for early prenatal detection of congenital heart disease.

Main Methods:

• Prospective review of 188 fetal echocardiograms from 8 to 15 weeks' gestation in healthy pregnancies.
• Inclusion of 10 pregnancies with severe fetal heart disease for comparison.
• Measurement of the cardiac axis in the four-chamber view in the axial plane.

Main Results:

• The mean cardiac axis increased significantly from 8-9 weeks (25.5°) to 10-11 weeks (40.4°).
• A stable leftward cardiac axis was observed from 12 weeks (49.2°) through 14 weeks (48.6°).
• Abnormal cardiac axis measurements (>90th or <10th percentile) were noted in some cases of congenital heart disease prior to 15 weeks.

Conclusions:

• The embryonic cardiac axis undergoes levorotation in late first trimester, establishing a stable leftward position by 12 weeks.
• This normal axis orientation persists until at least 14 weeks and 6 days.
• Abnormal cardiac axis findings may aid in the prenatal diagnosis of severe congenital heart disease.