To what extent do the presentation of fetus, amniotic fluid index and fetal weight at term affect the cardiac axis?

OBJECTIVE

To analyse the change in cardiac axis with advancing gestational age and the factors that may affect it.

METHODS

45 healthy pregnant women in 20th weeks of gestation were enrolled to the study. The cardiac axis was noted for each participant. The same group was once more assessed at term and the change in cardiac axis was calculated with the difference of cardiac axis at term and the 20th gestational weeks. Change in cardiac axis with advancing gestational weeks and factors that may affect it such as amniotic fluid index (AFI), estimated fetal weight (EFW) at term, actual birth weight and presentation of the fetus at term were evaluated.

RESULTS

The median of ages was 28.0 (IQR=12.0)years within a range of 18-39years. The median of change in cardiac axis was 11.0 (IQR=9.0) degrees within a range of 3.0-47.0 degrees. The change in cardiac axis in regard to the fetal presenting part was 11.0 (IQR=8.0) degrees in vertex presentation and 23.50 (IQR=21.0) degrees in breech presentation. 81.1% of the variation in change in cardiac axis was found to be due to the actual birth weight and fetal presentation, with each 100g increase in actual birth weight leads to an increase of 0.375 degrees in cardiac axis.

CONCLUSION

EFW at term, presentation of the fetus and the actual birth weight were all found to be significant in predicting the change in cardiac axis, but not AFI. These findings may have future potential value in evaluating electrocardiogram (ECG), especially of pregnants with extremes of left axis deviation (polyhydramnios, large fetus or breech presentation). Clinicians should be cautious during the interpretation of the ECG in pregnants, especially in those with extremes of left axis deviation because of either polyhydramnios, large fetus or breech presentation.