This entry will deal with the infection caused by cytomegalovirus, or CMV, which is a lot easier to write and say, right?
You really should know that a cytomegalovirus infection is the most frequent congenital infection during pregnancy. It occurs more than Zika and HIV combined, and even so, it’s still misunderstood by parents.
In most cases, the cytomegalovirus (CMV) is harmless for infected individuals. However, under certain conditions, it can lead to severe infections with significant consequences. This includes individuals with weakened immune systems, those who have undergone transplants, and pregnant women. This discussion focuses on the case of pregnancy, exploring the effects of a CMV infection during this period, as well as the potential impacts on the expectant mother and the risks of congenital or neonatal infection for the baby.
Today, it is known that many congenital defects in babies are caused by CMV infections. Sharing information about this infection is crucial to help recognize the symptoms and understand the preventive measures that can be taken.
Defining Cytomegalovirus
Cytomegalovirus part of the same family as herpes. Some define it as “Human Herpes Virus 5” (Health Canada: Herpes Simplex Virus 5). This infection’s characteristics are very similar to those in the same family. These include infectious mononucleosis, roseola, chicken pox and Zona.
CMV Infection Risks
The number of infected people increases with age. The literature shows that the general risk of contracting CMV is 24% for parents with young children, 8.5% for healthcare and daycare workers, and 2.3% for pregnant women. When our immune defences are lowered (stress or exhaustion), we are more exposed to infection. Don’t forget that a pregnant woman’s immune system is more vulnerable in the last trimester of pregnancy, putting her at greater risk of all kinds of infections, including CMV.
Even if infection mostly occurs at a young age (children under three years of age), 60% to 90% of adults (men and women) have “anti-CMV” antibodies in their blood. This means that they’ve been infected at some point in their lives. Most of these people, if healthy, will have no symptoms of this benign infection. For the most part, the virus will always remain inactive, dormant or latent.
CMV Transmission
It’s important to highlight that before infecting someone, you have to have been in contact with the virus previously, infected after its incubation period. You can then transmit it to someone else.
During pregnancy, the mother’s fetal transmission risk starts during the first trimester. The transmission risk to the baby is 36.4% in the first trimester, 40.1% in the second trimester and 65% during the last trimester.
How can someone get infected by cytomegalovirus? Good question! Infection can happen many ways, normally with direct contact with organic or biological fluids or infected tissues.
- Saliva (cough, kissing)
- Tears
- Respiratory secretions
- Genital secretions (cervical, sperm)
- Urine and stool
- In utero through the placenta
- During birth when in contact with vaginal mucosa
- During transplants with infected organs
- Breast milk
- Blood transfusions.
Since the virus can live on a lifeless surface up to seven days in rare cases, CMV can be transmitted via infected objects like toys, cutlery, or a bottle nipple. This is why repeated contact with young children increases the risks of infection. They’re not independent, always in our arms. We feed them, wash them, change their diapers or wipe them when they go to the bathroom, blow their nose, etc.
CMV Diagnosis and Symptoms
How do you know if you’re already infected with cytomegalovirus?
Unfortunately, no very precise screening tests for the true presence of the infection exist. We don’t have clear recommendations about what you can do. Currently, recognised effective ways to treat this infection don’t exist. This is why public health officials don’t recommend systematic screening of CMV before or during pregnancy. However, doctors can ask for targeted monitoring for a pregnant woman, like they do when they have flu symptoms. A follow-up ultrasound can also examine the baby’s proper growth and the placental development in these circumstances. The SOGC criteria also suggest screening pregnant women for CMV if ultrasound scans show a possible problem in the fetal central nervous system with calcifications, or in the heart and/or abdomen.
A diagnosis of cytomegalovirus infection is possible, but limited, using blood tests (serology) to detect specific “anti-CMV” antibodies. This indicates a previous or new infection.
This analysis is more frequent for pregnant women and added to the doctor’s clinical exam and data collection.
Even if the symptoms are similar to mononucleosis, healthy subjects don’t have a sore throat when they are infected with cytomegalovirus, which differentiates the two infections.
Other more sophisticated ways to diagnose and screen for a previous or recent CMV infection exist, but they’re infrequent and variable from one country to another. At 21 weeks of pregnancy, some pregnant women can have an amniocentesis to take a sample of the amniotic fluid. This will check to see if the baby was infected in utero.
Newborn infection can occur in their mother’s uterus during any trimester of pregnancy. From 0.2% to 2.4% of babies will be infected congenitally. The CMV infection can also occur after birth through neonatal infection.
Most of the time the baby’s diagnosed with a urine or saliva test. These look for the presence of bacteria, germs and other agents possibly responsible for the infection. A saliva test is quicker, but if the baby has their mother’s milk in their mouth, she might be screened (through her milk) rather than her baby. For this reason, urine testing is still the most specific and sensitive method of screening newborns. Early diagnosis of CMV infection in newborns is very important, as treatment needs to be administered very quickly, within the first few weeks of life (ideally before 14 to 21 days), and for 6 months thereafter.
Cytomegalovirus Infection Symptoms
As I said earlier, 90% of infected healthy adults and children won’t have specific symptoms. This is why it’s a “silent” infection. But they may also have innocuous signs that aren’t specific to the infection. It might look like viral influenza, with some fever, headaches, general muscle and joint pain, general fatigue and swelling of certain lymph nodes noted during a clinical exam, similar to mononucleosis. In babies, there may be problems with eye or hearing tests, or evidence of neurological damage on postnatal assessment (e.g. microcephaly, convulsions). 5 to 15% of newborns may have sequelae of congenital CMV infection.
Cytomegalovirus During Pregnancy
Why are we concerned about a cytomegalovirus infection during pregnancy?
A cytomegalovirus (CMV) infection between a mother and her baby is one of the most frequent viral infections during pregnancy. If the mother is infected when young, the virus can be reactivated and lead to fetal problems. If the future mother is infected for the first time during her pregnancy (primary infection), this is even likelier. Half of babies will be infected through their mother’s blood in this case, and the impact will be more dramatic.
The more severe impact of primary infection in the mother can, in the worst cases, lead to pneumonia, duodenal ulcers, cervical infection or blindness.
At the start of pregnancy, the more severe impact of an infection for an in utero baby (congenital infection) can lead to termination or serious complications. Later in pregnancy, developmental delays, growth delays, premature birth, central nervous system defects, serious jaundice caused by kidney (hepatic) lesions, and deafness can occur. We think that 30% of defects in newborn babies are due to the CMV virus. Also, even if the baby is born without clinical signs, 6% to 25% of them will show neurological (mental or psychomotor delays) and sensorial (hearing loss) aftereffects within the first two years.
The possible impact of a CMV infection in a baby during the neonatal period, contracted after birth, can be just as serious, especially if they’re premature. The repercussions can vary depending on the specific affliction, with liver and blood complications for example.
CMV Treatment and Prevention
Given that a CMV infection in a healthy person will suddenly disappear or remain latent most of the time, antiviral treatments won’t be advised. Currently, treatments that diminish the risks of infection for a baby in utero are unavailable.
For serious illnesses, anti-CMV antiviral (immunoglobulin) medications exist, but their effectiveness hasn’t really been documented. For babies, they will be cared for by a multidisciplinary team using antiviral treatments and close paediatric monitoring. An audiology test will be performed to eliminate these types of afflictions.
Much is still unknown about cytomegalovirus infections during pregnancy, both for a baby in utero and a newborn infected during the neonatal period. Research continues to better understand the infection.
Preventing CMV
Approved vaccines to prevent the cytomegalovirus infection aren’t available, but vaccines are currently being tested. Vaccine research is advancing quickly since this infection is considered a health priority worldwide. A vaccine might be available soon for women without CMV antibodies (negative test meaning no infection) who want to become pregnant or starting a pregnancy. This will prevent contracting the infection during pregnancy and infecting the baby..
Since cytomegalovirus is often transmitted by children under three years of age, here are a few precautionary hygiene rules and other suggestions for pregnant women.
- Regularly wash your hands (also when changing diapers)
- Avoid placing your child’s objects in your mouth
- Avoid kissing children on the mouth
- Don’t take a bath with a child
- Avoid direct contact with an ill person
- Rest
- Use condoms when having sex during pregnancy
- Resting and reducing stress will help ensure your immune system works well to avoid a CMV infection.
When a pregnant woman regularly works in direct, repeated and frequent contact with young children she will go on automatic early leave.
Automatic leave can support pregnant women at higher risk of infection, such as those working in daycares with infants. This measure aims to reduce workplace-related infection risks through the “Safe Motherhood” health and safety program. Alternative tasks that adhere to preventative measures for pregnant women can also be considered.
Awareness about cytomegalovirus infections is essential to help prevent infection and safeguard both mother and baby from possible consequences.
Marie Fortier
The Baby Expert
Article updated : September, 2023.
