Predicting Neonatal Hypoxia in dTGA/IVS Remains Challenging, Heightens Need for High-Risk Delivery Planning

Christopher Lindblade, MD, co-author of a 2026 Journal of the American Society of Echocardiography study, shares how factors seen on fetal echocardiography support the Phoenix Children’s model for performing urgent bedside balloon atrial septostomy for babies with neonatal hypoxia.

By
October 15, 2026
7 min

Phoenix Children's Medical Connection

Overview

In a prospective, multicenter study of 132 mother-infant pairs with prenatally diagnosed dTGA/IVS, fetal echocardiographic measurements did not reliably identify which newborns would develop hypoxia or require urgent balloon atrial septostomy (BAS). Neonatal hypoxia occurred in 38% of infants, and the study authors state that delivery planning should anticipate possible hypoxemia and urgent BAS for every prenatally diagnosed infant with dTGA/IVS.

Background

Dextro-transposition of the great arteries (dTGA) accounts for 5–7% of congenital heart disease, and inadequate mixing in dTGA with an intact ventricular septum (IVS) can cause severe hypoxemia and hemodynamic compromise after birth. BAS may be required shortly after delivery to improve systemic oxygenation and bridge the infant to arterial switch surgery. Prenatal identification of infants likely to need BAS has been difficult; previously examined markers, including atrial septal mobility and ductal flow patterns, have not reliably predicted the need for intervention. A prior study cited in the article found that placing a BAS intervention team at the delivery bedside can shorten time to BAS.

Data Highlights

Study measure	Finding
Design and enrollment	Prospective, observational, multicenter study; 132 mother-infant pairs from 23 North American institutions, enrolled 2019–2022
Neonatal hypoxia	38% of infants developed hypoxia, defined as PaO2 <30 mmHg or SpO2 <75%
BAS among infants with hypoxia	Approximately 61% underwent BAS; nearly 88% of procedures were considered urgent
BAS among infants without hypoxia	51% underwent BAS; 88% of procedures were considered urgent
Prenatal assessment	Third-trimester fetal echocardiography included foramen ovale-to-total septal length ratio, septum primum angle, atrial septal excursion ratio, and atrial septal hypermobility; no finding reliably identified infants who would remain stable after birth

Key Findings

The study enrolled 132 mother-infant pairs with dTGA/IVS at 23 North American institutions between 2019 and 2022.
Investigators assessed third-trimester fetal echocardiographic measurements, including foramen ovale-to-total septal length ratio, septum primum angle, atrial septal excursion ratio, and atrial septal hypermobility.
Neonatal hypoxia was defined as PaO2 below 30 mmHg or SpO2 below 75%; 38% of infants met this definition.
Approximately 61% of infants with hypoxia underwent BAS, and nearly 88% of those procedures were considered urgent.
BAS was also performed in 51% of infants without hypoxia; 88% of these procedures were considered urgent, illustrating that fetal findings both missed and overcalled the need for intervention.
The study authors concluded that no fetal echocardiographic finding reliably predicted neonatal hypoxia and stated that all infants with prenatally diagnosed dTGA/IVS warrant delivery planning that anticipates possible hypoxemia and urgent BAS, even when fetal echocardiography appears reassuring.

Clinical Implications

The study authors advise planning delivery for every prenatally diagnosed dTGA/IVS infant with the possibility of significant hypoxemia and urgent BAS in mind, regardless of reassuring fetal echocardiographic findings. They note that hospitals without round-the-clock pediatric cardiology or BAS resources can plan in advance to ensure coverage at delivery.

Conclusion

In this multicenter cohort, fetal echocardiography did not provide reliable prenatal prediction of neonatal hypoxia or urgent BAS in dTGA/IVS. The authors emphasize high-risk delivery planning for all affected infants.