Efficacy of fetal cardiac axis evaluation in the first trimester as a screening tool for congenital heart defect or aneuploidy

Abstract

Objective: To prove the efficacy of determining the abnormal fetal cardiac axis for screening congenital heart defects (CHDs) and predicting fetal aneuploidy at 11.0 to 13.6 weeks of pregnancy.

Methods: This retrospective study was performed at a single high-risk pregnancy center. The fetal cardiac axis was evaluated between 11.0 and 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. A CHD was confirmed based on the second- to third-trimester fetal status or postnatal imaging. Aneuploidy was diagnosed using chorionic villus sampling, amniocentesis, or genetic testing after birth. Fisher's exact test was performed to assess the association between the fetal cardiac axis and the abnormal fetal status. A 2-way contingence table analysis was performed to confirm the efficacy of the fetal cardiac axis as a screening tool.

Results: Among the 142 fetuses, 10 had a CHD while 17 had aneuploidy. The abnormal fetal cardiac axis was significantly associated with CHDs (P=0.013) and aneuploidy (P=0.010). None of the fetuses with CHDs or aneuploidy had an isolated abnormal cardiac axis alone without other sonographic findings. The sensitivity of the fetal cardiac axis was 50.0% for CHDs and 41.2% for aneuploidy.

Conclusion: The fetal cardiac axis can be an additional helpful tool for prenatal screening of CHDs and aneuploidy in the first trimester.

Keywords: Aneuploidy; Axis; Congenital heart defect; Fetal heart; First trimester.

Fig. 1. A schematic diagram of the cardiac axis measurement.

a, the line bisecting the thorax in the anteroposterior direction; b, the line tracing the long axis of the heart; L, left aspect of the fetus; R, right aspect of the fetus; P, posterior aspect of the fetus.

Fig. 2. Normal and abnormal fetal cardiac axes of fetuses in the first trimester observed using ultrasonography. Dotted lines are the lines bisecting the thorax in the anteroposterior direction. Full lines are the lines tracing the long axis of the heart. (A) Normal: 65.3° at 11.0 weeks. The fetus was delivered through a cesarean section at 39.0 weeks of gestation. (B) Left deviation: 75.4° at 12.4 weeks. Atrioventricular septal defect observed using fetal echocardiography. Trisomy 13: Fetal death in utero was diagnosed at 14.5 weeks of gestation. (C) Right deviation: 10.1° at 12.2 weeks. Ventricular septal defect, aortic stenosis, mitral atresia, and left ventricular hypoplasia observed using fetal echocardiography. Fetal death in utero was diagnosed 13.4 weeks of gestation.

L, left aspect of fetus; R, right aspect of fetus; P, posterior aspect of fetus.