Normal values of cardiac axis (CA) measurements in healthy fetuses during the first trimester screening ultrasound

To report the normal fetal cardiac axis (CA) values at the time of the first trimester screening ultrasound.

Standardized images and measurement of the CA were obtained from 100 healthy fetuses between 11+0 and 13+6 weeks of gestation along with the nucal thichkness (NT), Crown-rump length (CRL) and other measurements. We excluded cases with abnormal NT, later diagnosis of abnormalities, and suspected fetal cardiopathy during the pregnancy follow-up. Data analysis was performed after all the patients delivered and cardiopathy was excluded.

CA was measurable in all the cases. Higher CRL was associated with a decrease in the CA. The mean ± SD embryonic/fetal CA was 48±5,2°, ranging from 39 to 60°, The 2.5 percentile was defined at 40° and the 97.5 percentile at 59°. The Pearson test resulted in a significant correlation between CA and CRL with a coefficient R of 70% and p-value <0.01.

CA tends to decrease at the 11 to 13+6 gestational ages. We defined 2.5 and 97.5% curves for the normal values of CA in our Middle Eastern population. A larger study will be required to differentiate normal and abnormal values for the early detection of heart abnormalities.