VP49.01: The natural history of fetal cardiac axis change in the first trimester

Fetal cardiac axis after first trimester in normal heart is 45 +/- 20 degrees. With progressed ultrasound imaging and increased experiences of first trimester studies, it would be necessary to re-evaluate the change of cardiac axis in normal fetuses at early gestation. The purpose of this study was to evaluate the cardiac axis in normal fetuses during the first trimester, which lead to the early detection of congenital heart diseases (CHD). Indeed, it would lead to better understanding of early fetal heart. This retrospective study was performed at our hospital from 2019 to 2021. The fetal cardiac axis was evaluated between 11.1–13.6 weeks of gestation in 142 fetuses. The cardiac axis in a 4-chamber view was measured as the angle between the line tracing the long axis of the heart and the line bisecting the thorax in the anteroposterior direction. These data were evaluated in Spearman rank-difference correlation analysis. There was a very weak positive correlation between Crown–rump length (CRL) and cardiac axis in 142 fetuses (r = 0.199, p-value = 0.022). Regarding to gestational age, there was a positive trend with the cardiac axis (r = 0.162, p-value = 0.063). At earlier gestation such as 11 weeks, the cardiac axis was slightly smaller than others at later first trimester. The change of fetal cardiac axis at early first trimester might be from the midline to the left. With these nomograms, fetal cardiac axis can be an additional information for prenatal detection of CHD in the first trimester. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.