The tiny viruses with big consequences for maternal and fetal health
Pregnancy is a time of joyful anticipation, but it also brings heightened health concerns—particularly regarding viral infections that can pass from mother to unborn child. Among the most significant are cytomegalovirus (CMV), rubella virus, and herpes simplex virus type 2 (HSV-2). These seemingly unrelated viruses share a dangerous commonality: they can cross the placental barrier, potentially causing miscarriage, stillbirth, or lifelong disabilities in affected infants.
What makes these infections particularly concerning is that they often present with mild or no symptoms in pregnant women, making them difficult to detect without screening. Understanding these hidden threats, their transmission routes, and prevention strategies represents one of the most important aspects of modern prenatal care.
of births affected by congenital CMV worldwide 1
Cytomegalovirus is a member of the herpesvirus family and represents the most common congenital viral infection worldwide. This ubiquitous pathogen affects people of all ages, with infection rates ranging from 0.6% to 0.7% of births in developed countries and 1% to 5% in developing nations 1 .
CMV spreads through contact with infected body fluids such as saliva, urine, tears, and blood. For pregnant women, exposure often occurs through contact with young children, particularly in childcare settings where CMV shedding is common. Research has shown that among children under 3 years in childcare centers, the prevalence of CMV shedding in saliva or urine ranges from 10% to 70% 1 .
When CMV infects a developing fetus, the consequences can be devastating. Approximately 10% to 15% of infected infants show symptoms at birth, which may include microcephaly (abnormally small head), hepatosplenomegaly (enlarged liver and spleen), jaundice, and petechiae (small red spots under the skin) 1 .
The long-term effects are equally concerning. Among asymptomatic infants at birth, 10% to 15% will develop complications later in childhood, most commonly sensorineural hearing loss but also neurodevelopmental delays 1 . In fact, CMV is the leading infectious cause of birth defects and the most common non-genetic cause of hearing loss in children 1 3 .
Rubella, often called German measles, is typically a mild illness in children and adults but poses severe risks during pregnancy, particularly during the first trimester. The virus can cause miscarriage, stillbirth, or a constellation of severe birth defects collectively known as congenital rubella syndrome (CRS) 2 6 .
The timeline of infection is crucial—if rubella occurs before 10 weeks of gestation, up to 90% of fetuses may develop defects 6 . The risk decreases significantly with infections later in pregnancy, but concerns remain throughout all trimesters.
Infants born with congenital rubella syndrome may experience a range of lifelong health challenges, including:
Unlike CMV, rubella is preventable through vaccination. The measles-mumps-rubella (MMR) vaccine provides safe and effective protection against rubella. The CDC recommends that children receive two doses of MMR vaccine—the first between 12 and 15 months of age, and the second between 4 and 6 years 9 .
Herpes simplex virus type 2 is a common sexually transmitted infection that causes genital herpes. While it typically causes mild or asymptomatic infection in healthy adults, it poses significant risks during pregnancy and childbirth. The virus can be transmitted to newborns during delivery, particularly if the mother has an active outbreak 7 .
A recent study conducted in Cameroon revealed a high prevalence of HSV-2 antibodies among pregnant women, with 55.5% testing positive for either IgM or IgG antibodies. The IgG seropositivity rate was particularly high at 54.4%, indicating previous infection .
When transmitted to newborns, HSV can cause neonatal herpes, a serious condition with three main clinical presentations:
The good news is that these risks can be significantly reduced through appropriate medical management. "Maternal antiviral prophylaxis in late pregnancy has shown to reduce the frequency of active HSV outbreaks at delivery" 7 . For women with active genital lesions at the time of delivery, cesarean section can prevent transmission to the newborn.
| Virus | Transmission Routes | Key Prevention Strategies | Potential Fetal/Neonatal Effects |
|---|---|---|---|
| CMV | Body fluids (saliva, urine), sexual contact, congenital | Hand hygiene, avoiding contact with young children's bodily fluids | Hearing loss, vision problems, developmental delays, microcephaly |
| Rubella | Respiratory droplets, congenital | MMR vaccination before pregnancy | Deafness, cataracts, heart defects, developmental delays |
| HSV-2 | Sexual contact, perinatal transmission | Antiviral medication in late pregnancy, cesarean delivery if active lesions | Neonatal herpes, skin-eye-mouth disease, CNS involvement, disseminated disease |
To better understand how CMV affects pregnancy outcomes, researchers in China conducted a comprehensive retrospective study of 22,673 pregnant women between 2018 and 2024 3 . The study employed sophisticated diagnostic techniques to detect CMV DNA in amniotic fluid samples collected during mid-to-late pregnancy.
The laboratory methodology was particularly precise. Researchers used a human cytomegalovirus nucleic acid quantitative detection kit with PCR-fluorescence methods. As detailed in the study, "2 mL of amniotic fluid was centrifuged at 2000 × g for 10 min, followed by supernatant removal" before DNA extraction and amplification 3 . This meticulous approach ensured accurate detection of the virus.
Among the 22,673 pregnant women tested, 36 (1.59‰) tested positive for CMV DNA in their amniotic fluid 3 . The outcomes for these infected women were concerning:
The study also revealed concerning findings about fetal development. Prenatal imaging detected fetal abnormalities in 21 (58.3%) of the CMV-infected pregnant women 3 . These findings underscore the importance of screening and monitoring for CMV during pregnancy, particularly for women with suspected exposure or symptoms.
Quality antenatal care provides the foundation for identifying and managing viral infections during pregnancy. Research from Ghana has demonstrated that women who received high-quality antenatal care had significantly lower odds of delivering low birth weight babies and preterm babies 4 .
A study in the Tamale metropolis of Ghana found that only 25.2% of participants received high-quality ANC, despite almost universal ANC coverage in the country 4 . This highlights the importance of focusing on the content and quality of antenatal care, not just the number of visits.
Despite the serious consequences of these infections, awareness remains surprisingly low. "Global surveys with data up to 2020 suggest that <7% of adults and <40% of pregnant women have heard of CMV" 1 . This knowledge gap represents a significant missed opportunity for prevention.
While CMV, rubella, and HSV-2 pose significant risks during pregnancy, understanding these viruses empowers women to take proactive steps toward protection. Through awareness, preventive measures, and appropriate medical care, the dangers these infections present can be substantially reduced.
The research is clear: quality antenatal care that includes education about these infections, appropriate screening when indicated, and early intervention when necessary makes a meaningful difference in outcomes. As we've seen, simple measures like hand hygiene for CMV, vaccination for rubella, and antiviral therapy for HSV-2 can dramatically reduce risks to both mother and child.
If you're pregnant or planning a pregnancy, discuss these viral infections with your healthcare provider. Ask about your immunity status, appropriate preventive measures, and any concerns you may have. By working in partnership with your healthcare team, you can take important steps toward ensuring the healthiest possible outcome for both you and your baby.