This is a prospective pilot study to examine whether transient maternal hyperoxygenation is useful as a diagnostic test to more accurately detect TGA patients with poor vs. good neonatal intracardiac mixing of blood, based on the in-utero response to oxygen exposure. Acute maternal oxygen administration will transiently increase the fetal oxygen levels to those reached at birth with spontaneous breathing, thus simulating conditions that will naturally occur at the time of birth. Echocardiogram and MRI will be used to examine the effects on the fetal circulation. The prenatal findings will then be compared to the neonatal presentation.~The investigators postulate that conditions that predispose newborns to acute neonatal compromise will be detectable and distinguishable prior to birth by echocardiography, MRI, or by combining the findings of both exams.
This prospective study will examine whether transient maternal hyperoxygenation is useful as a diagnostic test to more accurately detect TGA patients with poor vs. good neonatal intra-cardiac mixing of blood, based on the in-utero response to oxygen exposure.