Larger lung volumes in fetuses with transposition of the great arteries and an intact ventricular septum compared to heart healthy fetuses and fetuses with transposition of the great arteries and a ventricular septal defect

BACKGROUND: Complex CHDs may impair organ development. One proposed mechanism is an altered relationship between blood flow, oxygen delivery, and subsequent organ growth. In this study, we examined whether fetal lung, intracranial, liver, and kidney volumes differ among fetuses with transposition of the great arteries with an intact ventricular septum, transposition of the great arteries with a ventricular septal defect, and healthy controls. METHODS: Eleven fetuses with transposition of the great arteries (6 with a ventricular septal defect and 5 with an intact ventricular septum) and 22 healthy controls were scanned between 1 and 3 times at gestational age 27-38 weeks, using fetal MRI. We measured lung, total intracranial, liver, and kidney volumes and compared fetuses with and without transposition of the great arteries while subsequently correcting for ventricular septal defect/intact ventricular septum status, estimated fetal weight, and gestational age, using mixed effects regression analysis. No difference was found in lung volume between fetuses with transposition of the great arteries+ventricular septal defect and controls. No significant differences in total intracranial, liver, and kidney volumes were found between transposition of the great arteries+ventricular septal defect, transposition of the great arteries+intact ventricular septum, and controls. CONCLUSION: In this preliminary study, late-gestation fetuses with transposition of the great arteries-intact ventricular septum had a 30% larger lung volume compared with both transposition of the great arteries-ventricular septal defect and healthy controls. Together with existing evidence of higher fetal pulmonary blood flow and increased oxygen saturation in transposition of the great arteries-intact ventricular septum, these findings support a potential link between blood flow, oxygen delivery, and organ growth.