A statewide law requiring cytomegalovirus testing for newborns who fail their hearing screen increased diagnoses more than fourfold, but still identified only a small fraction of infants actually born with the infection, according to new research in Pediatrics that its authors say makes the case for universal testing.
Congenital cytomegalovirus, abbreviated cCMV, is the most common infectious cause of birth defects and the leading non-genetic cause of hearing loss in infants in the United States. It affects roughly 1 in 200 newborns. Most infected children, about three-quarters, never develop complications. For the remaining quarter, consequences can include hearing loss, vision problems, epilepsy, learning disabilities, and cerebral palsy.
The practical stakes for parents are specific. Antiviral treatment can improve hearing outcomes, but it has to start within the first weeks of life. A diagnosis made at age two, after a toddler shows delayed speech, arrives long after that window has closed.
The Connecticut Experiment and What It Caught
Connecticut enacted a law in 2016 requiring CMV testing for all infants who failed their newborn hearing screen. Researchers led by Aanchal Wats and Carlos Oliveira at Yale School of Medicine analyzed 11 years of data, from 2013 through 2023, within a health system serving about 60% of the state's population, comparing the three years before the mandate with the eight years after.
Targeted screening increased confirmed cCMV diagnoses 4.3-fold. Among 197,177 babies born in the system over the study period, 49 had suspected or confirmed cCMV, and about two thirds of those had moderate to severe symptoms.
The limitation is arithmetic. Some infants who passed their newborn hearing screen were diagnosed later, only after symptoms emerged. Wats told Medscape that many children are still missed, especially those who appear well early on, while noting the mandate did identify infants with milder disease or isolated hearing loss who would likely not have been diagnosed otherwise. The authors concluded that a hearing-targeted approach alone is insufficient and that the findings support Connecticut's move to universal screening. A preprint version of the analysis describes the interrupted time series design in full.
The Diagnostic Window That Makes Timing Everything
CMV must be detected within the first 21 days of life to confirm congenital infection. After that point, a positive test cannot distinguish infection acquired before birth from infection acquired after, including through breast milk, which is common and generally harmless in full-term infants.
That 21-day boundary is why screening has to happen at birth rather than at the first sign of a problem. Testing uses polymerase chain reaction on saliva, urine, or dried blood spots, with a positive saliva result typically confirmed by urine or blood testing.
The clinical reason for urgency compounds the diagnostic one. Some infants with cCMV are born with hearing loss, but another 20% to 25% develop it later in childhood, and clinicians have no reliable way to predict which children those will be. Identifying infected infants at birth allows audiology monitoring on a schedule rather than by chance.
The Argument in the Accompanying Commentary
An editorial published alongside the study made the policy case directly, arguing that cCMV remains underdiagnosed without systematic universal screening and that growing policy momentum supports newborn testing. Organizations including the American Academy of Audiology, the American Society of Otolaryngology-Head and Neck Surgery, and the American Cochlear Implant Alliance recommend universal cCMV screening.
Megan Pesch of the University of Michigan, a co-author of the commentary and director of a CMV developmental follow-up clinic, told CIDRAP that targeted testing catches only a fraction of affected infants, roughly 7% of all babies with CMV. She said universal screening would find substantially more, while also identifying children who will never develop symptoms, which she acknowledged is a sticking point for many. The commentary discusses using the dried blood spot already collected during routine newborn screening, the heel stick every U.S. newborn receives, as the delivery mechanism.
Pesch also described what earlier diagnosis buys. Antiviral treatment started in time can lower viral load and inflammation and has been shown to improve hearing outcomes, slowing or arresting hearing loss during the period when speech develops. She was equally clear about its limits: the antiviral addresses hearing and does not affect a child's risk of cerebral palsy, epilepsy, vision problems, or learning disabilities.
Not every question is settled. Dried blood spot testing has lower analytical sensitivity than saliva testing, meaning it misses some true infections, and the optimal universal method is still debated. Universal screening also identifies infants who will never develop problems, which raises questions about parental anxiety and follow-up costs that health systems have to plan for.
The State Policy Map Parents Are Navigating
Only two states currently screen newborns for cCMV. Minnesota became the first to mandate universal screening. Connecticut began universal screening in July 2025 after years of advocacy by families, and roughly 70 infants with cCMV have been identified through the panel in its first year.
Advocates want the condition added to the federal Recommended Uniform Screening Panel, which currently covers 38 conditions tested from the newborn blood spot, so that states do not have to act one at a time. That path became harder in 2025, when the Department of Health and Human Services disbanded the advisory committee that reviewed evidence and recommended conditions for the panel.
The result is that whether a baby is tested depends substantially on the state of birth.
What Expecting and New Parents Can Do
If you are pregnant or planning to be, ask your obstetric clinician about CMV. The virus spreads through saliva, and pregnant people most often contract it from a toddler who picked it up at daycare. Prevention guidance focuses on reducing contact with saliva and urine from young children: not sharing utensils, cups, water bottles, or food with toddlers, avoiding putting a child's pacifier in your mouth, and washing hands after diaper changes.
If your baby was born in a state without universal screening and you want testing, ask the pediatrician within the first three weeks of life. After 21 days, the test cannot establish congenital infection.
If your infant is diagnosed, ask for referral to pediatric infectious disease and to audiology. Treatment decisions, including whether antiviral therapy is appropriate, depend on the severity of findings and are best made by specialists.
If your child passed a newborn hearing screen but is not meeting speech or language milestones, raise it promptly. Passing at birth does not rule out later hearing loss, and early intervention services exist in every state.
Frequently Asked Questions
What is congenital CMV? An infection passed from a pregnant person to the fetus, affecting about 1 in 200 newborns. It is the leading non-genetic cause of infant hearing loss and the most common infectious cause of birth defects.
What did the study find? Connecticut's hearing-targeted screening law increased confirmed diagnoses 4.3-fold, but researchers found that infants who passed their hearing screen were still being diagnosed later, after symptoms appeared.
Why does testing have to happen so early? Congenital infection can only be confirmed within the first 21 days of life. After that, a positive test cannot distinguish infection before birth from infection acquired afterward.
Can it be treated? Antiviral therapy started early can improve hearing outcomes in eligible infants. It does not change the risk of cerebral palsy, epilepsy, vision problems, or learning disabilities. Treatment decisions belong to pediatric infectious disease specialists.
Which states screen universally? Minnesota was first to mandate universal screening, and Connecticut began universal screening in 2025. Those are currently the only two states that screen.
How can pregnancy risk be reduced? Avoid contact with saliva and urine from young children, do not share utensils, cups, or food with toddlers, and wash hands after diaper changes. Discuss specifics with your obstetric clinician.
My baby passed the hearing test. Are we clear? Not necessarily. Between 20% and 25% of children with cCMV develop hearing loss later in childhood. Raise any speech or language delays with your pediatrician.
