Monochorionic monoamniotic (MCMA) twin pregnancies are typically delivered at 32–34 weeks of gestation to reduce the risk of intrauterine demise, but this practice may compromise outcomes for a growth-restricted or very–low-birth-weight twin requiring complex cardiac surgery. We conducted a literature review in Cochrane Central Register of Controlled Trials, EMBASE and PubMed from inception to October 26, 2025. We included reports of MCMA twin pregnancies with one fetus with TGA describing perinatal outcomes, cord complications, and cardiac surgery in very–low-birth-weight neonates. Of 388 records identified, 302 abstracts were screened, 54 full texts reviewed, and 8 studies were included. Only five published cases of MCMA with one twin affected by transposition of the great arteries were identified: two in conjoined twins, one with postmortem diagnosis after extreme prematurity, and two operated cases, of whom just one survived. We describe to our knowledge the third non-conjoined MCMA twin pregnancy with TGA and only the second postoperative survivor, delivered at 34 weeks. Systematic reviews have suggested that, in otherwise stable MCMA pregnancies with TGA, prolonging gestation to at least 33 weeks is considered safe, and based on our experience we suggest that prolonging pregnancy to 34 weeks may still be beneficial, but multicenter data is needed to reach this conclusion.
Montoya et al. (2026) studied this question.