Newborns with transposition of the great arteries (TGA) are at risk of severe hypoxia from inadequate atrial mixing, closure of the arterial duct, and/or persistent pulmonary hypertension of the newborn (PPHN). Acute maternal hyperoxygenation (AMH) might assist in identifying at-risk fetuses. We report pulmonary vasoreactivity to AMH in TGA fetuses and its relationship to early postnatal hypoxia and requirement for emergency balloon atrial septostomy (e-BAS).

Standard fetal echocardiographic (FE) assessment of the foramen ovale (FO): to total septal length and morphology of flap valve of the FO were used to predict the need for e-BAS. Following prospective recruitment, additional assessments were performed in fetuses with TGA at baseline and repeated after 10 minutes of 10 L/min of 100% oxygen delivered via non-rebreather mask to the pregnant mother. Analysis included measurement of atrial septal excursion, branch pulmonary artery pulsatility index (PA PI), middle cerebral artery (MCA) PI, and cardiac output. Delivery and newborn status were reviewed. Hypoxia was defined as preductal oxygen saturations <75% and e-BAS when undertaken within 2 hours of birth. Area under receiver operating characteristics curves were calculated.

Thirty cases underwent FE at 34.6 weeks’ gestation (interquartile range, 34.6-35.6). All 7 predicted to require e-BAS based on standard FE were correctly identified prenatally. Three of 30 were hypoxic without FO restriction and treated with nitric oxide (PPHN). Change in PA PI ≤ 15% was associated with PPHN (P = .001) but not with e-BAS. The MCA PI response to AMH varied according to newborn condition, a mean reduction occurred in the non-hypoxic newborns (−7.8 ± 18.3, P = .05). Increase in MCA PI Z score (area under receiver operating characteristics curves; 0.837; 95% CI, 0.663-1.00, P = .01), reduction in right ventricular cardiac output (0.811; 95% CI, 0.623-0.998, P = .04), and reduction in combined cardiac output (0.851; 95% CI, 0.699-1.0, P = .01) were moderately associated with e-BAS. Changes in atrial septal excursion and FO flow direction with AMH did not correlate with newborn condition.

A PA PI change ≤15% to AMH was associated with postnatal hypoxia due to PPHN. Increase in right and combined cardiac output and reduced MCA resistance with AMH are seen in those who do not require e-BAS.

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