When a Baby Is Born With Congenital CMV: What 20 Years of Hearing Records Tell Us About Antiviral Treatment

A long-running Japanese study followed children with congenital cytomegalovirus for up to 15 years to see how their hearing changed over time, with and without early medication

A new 15-year Japanese study followed 56 children born with congenital cytomegalovirus (CMV) to see how their hearing changed depending on whether they received antiviral medication as newborns. Treated children had smaller, earlier hearing declines that then stabilized, while untreated children faced repeated hearing loss for years, sometimes into the teens — a reminder that every child with congenital CMV needs long-term hearing follow-up, not just a normal result at birth.

A virus most parents have never heard of, and a problem doctors have long struggled to solve

Cytomegalovirus, or CMV, is a common virus that most adults carry without ever knowing it — it usually causes no symptoms, or something that feels like a mild cold. The trouble comes when a pregnant person passes the virus to their baby before birth, which is called congenital CMV. It happens more often than most people realize, and it is actually the single most common cause of hearing loss in children that is not inherited genetically. A newly published study from Japan's National Center for Child Health and Development [1] followed 56 children with congenital CMV for up to 15 years to see how their hearing changed depending on whether they were treated as newborns — the longest real-world look yet at a question doctors have been trying to answer for two decades. For most of that time, doctors had no good options for a baby born with obvious signs of infection — a small head, calcium deposits visible on brain imaging, or hearing loss detected right at birth. That began to change when researchers in the United States tested an antiviral medicine called ganciclovir, given through an IV line, and found it could improve hearing in sick newborns — though the drug caused serious side effects, including dangerously low white blood cell counts, that limited how widely it could be used [2]. A later study tested a pill version of a related drug, called valganciclovir, and found that six months of treatment worked better than six weeks, which is why six months became the standard length of treatment still used today [3]. Doctors in Japan later confirmed that the same dose — taken twice a day — worked well for Japanese infants too, setting the stage for the hospital where this new study took place to begin using it routinely [4]. Newborn hearing screening, now standard in most hospitals, is part of why congenital CMV is caught as early as it is, since CMV is behind an estimated one in five to one in four cases of hearing loss found in newborns and young children [5]. But even with treatment established, one big question remained unanswered: does the benefit measured in the first months or couple of years actually last? An earlier study that followed children with congenital CMV for a full decade found that about 1 in 5 developed hearing loss with lots of ups and downs, especially in the early years, no matter whether they had been treated [6] — which is exactly the puzzle this new, even longer study set out to untangle.

What researchers looked at, and who they compared

Researchers at Japan's National Center for Child Health and Development in Tokyo reviewed 20 years of records — 2004 through 2022 — and identified 66 children born with congenital CMV. After excluding 10 who had not had a standard newborn hearing test, they were left with 56 children (112 ears, since hearing is measured and can be affected in each ear separately) who had at least two years of hearing follow-up, with some followed for as long as 15 years [1]. Nineteen of these children had received antiviral medicine — the pill form, the IV form, or a combination — started within their first two months of life, because they showed at least moderate signs of the infection at birth, such as a smaller head size or hearing loss already present. The other 37 children did not receive medication, either because they had no symptoms at birth, had only mild symptoms, or were not diagnosed in time for treatment to be started within the usual window. It matters a great deal that doctors — not a coin flip — decided who got treated: the treated children started out sicker on average, with more brain-imaging findings and developmental concerns already present at birth. That means this study cannot prove that medication alone caused any differences seen later; it can only show what happened to two groups of children who looked different from the start.

What happened to their hearing over the years

By the end of the study, about the same share of children in each group had some hearing loss — roughly 7 in 10 either way — which might sound discouraging at first. But looking more closely at how much hearing changed, and when, tells a more encouraging story about treatment. Ears in the treated group were about half as likely to show a significant hearing decline (26% versus 41% of ears), and when hearing did get worse, it worsened by about half as much on average as in untreated children. The timing was the most striking difference: treated children who lost hearing almost always did so before age 3, and then their hearing generally stayed put — only one exception was recorded in the whole group. Untreated children, by contrast, were more likely to lose hearing after age 3 (typically around age 3½), and to keep losing hearing in repeated episodes for years afterward — with some episodes recorded as late as age 17. A few children on medication had side effects, including low potassium, low white blood cell counts, or elevated bilirubin (a sign of liver stress), which led doctors to stop treatment early in 4 of the 19 treated children — all within the first two months of treatment. Reassuringly, none of these children went on to lose additional hearing after treatment was stopped.

How this fits with what else is known

This study adds real-world detail to a research landscape that has, honestly, been difficult to pin down. One earlier study of treated children found that the share with stable or improved hearing kept climbing between six months and three years after treatment [4], which fits with the idea that treatment helps hearing settle down early. Another earlier study found that hearing loss could keep progressing for years regardless of treatment, and warned that studies which stop checking too soon will underestimate how much decline happens later [7] — a caution this new 15-year study was specifically designed to address. Two attempts to test treatment more rigorously, through large research trials — one in babies with hearing loss but no other symptoms, another in babies diagnosed after one month of age — both struggled to enroll enough families to reach a clear answer, which shows just how hard this particular question is to study directly [8][9]. One of those efforts, the ValEAR trial in the United States, had to stop its treatment study early for that reason, though it went on to produce useful information about how CMV testing is actually being done across dozens of American hospitals [9]. A separate study in the Netherlands did find that six weeks of the pill medication reduced hearing decline in babies who had hearing loss but no other visible symptoms of CMV [10] — a group that is not always offered treatment today. The same Japanese research team behind the medication dose used in this study has also published newer follow-up papers looking at hearing at three years [11] and overall child development at four years [12]; the development follow-up found that even among treated children, about 3 in 10 still had a developmental delay by age four — an important reminder that treatment helps with hearing specifically but is not a cure-all for every way this infection can affect a child.

What this means for families

If your baby has been diagnosed with congenital CMV, this study offers two reassuring — and two sobering — messages. First, if your child was treated with antiviral medication as a newborn, hearing that has been stable for a few years is a genuinely good sign, though your child's hearing care team may still recommend periodic checks as a safety net. Second, if your child was not treated — whether because symptoms were mild, absent, or discovered later — this study is a strong reminder not to let hearing checks lapse after the early years, since new hearing loss showed up well into the school-age years and even adolescence in the untreated children studied here. Every child born with congenital CMV, regardless of whether they received medication, benefits from a long-term plan for hearing checks rather than a short list of newborn tests. If you have questions about your own child's treatment history or surveillance schedule, your pediatrician or an audiologist familiar with congenital CMV is the right person to help you build that plan. For background on how congenital CMV is first identified, or on pregnancy-prevention efforts, see In[Neo]Sight's companion articles on newborn screening for congenital CMV and antenatal prevention of congenital CMV.

What researchers are working on next

Because this study looked backward at records from children who were already treated differently by their own doctors, it cannot definitively prove that medication caused the better hearing patterns seen in treated children — only that the two groups' outcomes looked different. Researchers are now working toward larger, forward-looking studies that would follow children from birth with a more carefully matched comparison, and that would track children well into the teenage years rather than stopping at two or three years, to figure out exactly which babies benefit most from early treatment and how long hearing monitoring should really continue.

References

  1. Morimoto N, Suzuki N, Imamura K, Saikawa T, Miyoshi N. Long-Term Outcomes in Children With Congenital Cytomegalovirus Infection. Laryngoscope Investigative Otolaryngology. 2026;11(2):e70386. doi:10.1002/lio2.70386 ↩
  2. Kimberlin DW, Lin CY, Sánchez PJ, et al. Effect of ganciclovir therapy on hearing in symptomatic congenital cytomegalovirus disease involving the central nervous system: a randomized, controlled trial. Journal of Pediatrics. 2003;143(1):16-25. doi:10.1016/S0022-3476(03)00192-600192-6) ↩
  3. Kimberlin DW, Jester PM, Sánchez PJ, et al. Valganciclovir for Symptomatic Congenital Cytomegalovirus Disease. New England Journal of Medicine. 2015;372(10):933-943. doi:10.1056/NEJMoa1404599 ↩
  4. Morioka I, Kakei Y, Omori T, et al. Oral Valganciclovir Therapy in Infants Aged ≤2 Months With Congenital Cytomegalovirus Disease: A Multicenter, Single-Arm, Open-Label Clinical Trial in Japan. Journal of Clinical Medicine. 2022;11(13):3582. doi:10.3390/jcm11133582 ↩
  5. Morton CC, Nance WE. Newborn Hearing Screening — A Silent Revolution. New England Journal of Medicine. 2006;354(20):2151-2164. doi:10.1056/NEJMra050700 ↩
  6. Foulon I, Naessens A, Faron G, Foulon W, Jansen AC, Gordts F. Hearing thresholds in children with a congenital CMV infection: A prospective study. International Journal of Pediatric Otorhinolaryngology. 2012;76(5):712-717. doi:10.1016/j.ijporl.2012.02.026 ↩
  7. Lanzieri TM, Caviness AC, Blum P, Demmler-Harrison G; Congenital Cytomegalovirus Longitudinal Study Group. Progressive, Long-Term Hearing Loss in Congenital CMV Disease After Ganciclovir Therapy. Journal of the Pediatric Infectious Diseases Society. 2022;11(1):16-23. doi:10.1093/jpids/piab095 ↩
  8. Kimberlin DW, Aban I, Peri K, et al. Oral Valganciclovir Initiated Beyond 1 Month of Age as Treatment of Sensorineural Hearing Loss Caused by Congenital Cytomegalovirus Infection: A Randomized Clinical Trial. Journal of Pediatrics. 2024;268:113934. doi:10.1016/j.jpeds.2024.113934 ↩
  9. Orb QT, Pesch MH, Allen CM, et al. Congenital Cytomegalovirus Testing Outcomes From the ValEAR Trial. Otolaryngology–Head and Neck Surgery. 2024;170(5):1430-1441. doi:10.1002/ohn.670 ↩
  10. Chung PK, Schornagel FAJ, Soede W, et al. Valganciclovir in Infants With Hearing Loss and Clinically Inapparent Congenital Cytomegalovirus Infection: A Nonrandomized Controlled Trial. Journal of Pediatrics. 2024;268:113945. doi:10.1016/j.jpeds.2024.113945 ↩
  11. Morioka I, Kakei Y, Imai T, et al; Japanese Congenital Cytomegalovirus Study Group. Three-year hearing outcomes in infants with congenital cytomegalovirus disease treated with oral valganciclovir: Interim results of a six-year follow-up study in Japan. Journal of Clinical Virology. 2025;177:105778. doi:10.1016/j.jcv.2025.105778 ↩
  12. Kakei Y, Morioka I, Imai T, et al; Japanese Congenital Cytomegalovirus Study Group. Four-year neurodevelopmental outcomes in infants with symptomatic congenital cytomegalovirus disease treated with oral valganciclovir: A prospective follow-up study in Japan. Brain and Development. 2026;48(3):104539. doi:10.1016/j.braindev.2026.104539 ↩