ObjectiveCongenital cytomegalovirus infection is the leading nonhereditary cause of pediatric sensorineural hearing loss. This systematic review evaluated infection concordance and comparative hearing abilities in twins/multiple births to model infection patterns.Databases ReviewedPubMed, Embase, Web of Science, and Google Scholar.MethodsStudies that reported hearing outcomes of congenital cytomegalovirus infection in at least one multiple birth were eligible. Concordant infections (both twins) and discordant infections (single twin) were included. Multiple reviewers performed data extraction and quality assessment. Analyses involved relative risk of infection concordance by zygosity and chorionicity and odds of hearing loss by infection concordance. Hearing outcomes were compared between siblings.ResultsOf 247 studies screened, 31 were included (74.2% high quality). The review captured 40 eligible multiple births. Among infected patients, 42.9% (95% confidence interval, 31.2–55.2%) demonstrated hearing loss. All uninfected twins had normal hearing. Most infections were concordant, and infected patients experienced 4.11 (1.18–14.36) times greater odds of hearing loss if their twin was also infected (p = .02). Yet siblings’ hearing outcomes diverged in over 40% of concordant cases. If either twin is infected, infection risk in the second twin is 3.25 (1.83–5.79) times greater in monozygotic than dizygotic twins and 2.50 (1.61–3.88) times greater in monochorionic than dichorionic twins (both p < .001). We describe a case from our practice.ConclusionCongenital cytomegalovirus infection patterns and hearing outcomes can vary widely even within a shared fetal and postnatal environment. Suspected infection in a twin indicates that both should receive testing and continued monitoring for late-onset sequelae.

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