Cytomegalovirus (CMV) in pregnancy

By trimester

Weeks 1–13

1st trimester

A first infection now is less likely to reach the fetus, around 30 percent, but tends to matter more when it does, with a higher chance of effects on the brain, hearing, and vision.

Weeks 14–27

2nd trimester

Transmission rises to roughly 45 percent with a primary infection in this window. If you have a toddler at home or work in childcare, this is the stretch where the saliva and handwashing habits do the most work.

Weeks 28–birth

3rd trimester

Transmission is highest now, around 72 percent, though infection this late is less often linked to severe effects. Hearing follow-up after birth is part of the standard picture for any baby with congenital CMV.

What does the evidence show for cytomegalovirus?

• More than half of people in the United States carry CMV by age 40, and 1 in 3 children have it by age 5, so it is one of the most widespread viruses in circulation. 1
• CMV spreads through contact with saliva, semen, vaginal fluids, blood, urine, tears, feces, or breast milk, and most people who have it never notice symptoms. 1
• With a first CMV infection during pregnancy there is about a 1 in 3 to 2 in 5 chance the virus passes to the fetus, and congenital CMV can cause vision problems, an enlarged liver or spleen, small head size, and nervous system effects. 1
• Transmission with a primary infection climbs with gestational age, from about 30 percent in the first trimester to 45 percent in the second and 72 percent in the third, and roughly 10 to 15 percent of congenitally infected babies show signs at birth. 2
• The behavioral steps studied for lowering exposure are avoiding saliva contact when kissing young children, not sharing food, utensils, drinks, or toys used by toddlers, and washing hands thoroughly after contact with young children. 2

When should I call my provider about cytomegalovirus?

Most CMV infections cause no symptoms, but when they do, expect a mono-like illness: fever, tiredness, muscle aches, sore throat, or swollen glands, usually with nothing that points specifically to CMV over any other virus. Tell your provider about any unexplained fever or glandular-fever-type illness so it can be evaluated and timed correctly, since amniotic fluid testing needs at least 8 weeks after a maternal infection to be accurate. A known exposure, such as a confirmed CMV infection in a child you care for, is also worth reporting even without symptoms of your own. None of these lists replace your own judgment: if this symptom worries you, that on its own is enough reason to check in with your healthcare provider.