Updated at 4:35 pm ET on June 13, 2023
An exhaustive list of things women are told to avoid during pregnancy includes cat litter, alfalfa sprouts, cooked meat, egg yolk, hamsters, sushi, herbal tea, gardening, Brie cheeses, aspirin, meat with pink, hot . pots. The chances of any of these harming the baby are slim, but why risk it?
Yet few doctors in the US tell pregnant women about the risk of contracting a common virus called cytomegalovirus, or CMV. The name may be unfamiliar, but CMV is the cause of disease of birth defects in America—before toxoplasmosis from cat litter or viruses from hamsters. Surprisingly, most babies infected with the virus in the womb are not affected, but they are suspected 400 people born with CMV die each year. Thousands more end up with hearing loss, epilepsy, developmental delays, or microcephaly, in which the head and brain are too small. Why the virus affects some children but not others is unknown. There is no medicine and no vaccine.
Amanda Devereaux’s youngest child, Pippa, was born with CMV, which damaged her brain. Pippa is prone to seizures. He couldn’t walk until he was 2 1/2 years old, and he didn’t speak by age 7. “I was just surprised that no one told me about CMV,” says Devereaux, who is now program director of the National CMV Foundation, which promotes awareness of the virus. The non-profit was founded by parents of children with congenital CMV. “Every one of them says, ‘Why didn’t I hear this?'” Devereaux told me.
One reason doctors hesitate to spread the disease is that the best way to prevent the virus is to avoid young children who have the virus. CMV symptoms are usually mild to absent in healthy adults and children. Young children, who often pick up CMV at day care, can continue to shed the virus in their body fluids for months or years when they are healthy. “I’ve met a class of two-year-olds where every child sheds CMV,” Robert Pass, a retired pediatrician and longtime CMV researcher at the University of Alabama, told me when we spoke in 2021.
This creates a common picture of congenital CMV: A babysitter brings CMV home and infects the mother, who is pregnant with her younger sibling. A recent study found that congenital CMV approx twice as common in second-borns than first-borns. Devereaux’s youngest child was in the hospital when she was pregnant. He told me: “I was sharing food with him because he never finished his breakfast.” Little did she know that her half-eaten muffin could harm her unborn daughter. Looking back, she says: “I wish I had less time to worry about not eating good meat and more time to think. Hey, I have this little babysitting job. I am at risk for CMV.“
CMV is a complicated virus because few things about it are certain. A mother cannot completely avoid her little child. Most pregnant women who are infected with CMV do not transmit it to their babies. Most children with the virus get better. Doctors warn patients about the many dangers of pregnancy—see the list above—but in this case, thousands of parents are blindsided by a very common virus every year. No one has a perfect answer for how to stop it.
Day care centers have been known as hot spots for CMV since at least the 1980s, when Pass, in Alabama, and some researchers in Virginia They started following newborns back to the nursery. The virus is rampant in lunch baskets for the same reason other viruses are rampant in daycare centers: Young children are born with no immune system, and they don’t make much effort to avoid each other’s saliva, urine, nose, and tears, all of that. . those with CMV. Among mothers with babies who have the virus in the hospital, one-third of mothers who have never had the virus get it within a year. And getting CMV for the first time during pregnancy is a very dangerous situation; These so-called early diseases are likely to cause serious problems for the unborn child. But recent research has found that reinfections and reactivations of the virus can cause severe CMV infection. (CMV remains in the body indefinitely after an initial infection, such as chicken pox, caused by an infectious virus.)
Therefore eliminating the risk of congenital CMV is impossible. But some CMV experts recommend giving women a short list of actions to reduce their risk during the nine months of pregnancy: Avoid sharing food or utensils with young children when caring for children; kiss the top of the head instead of the mouth; wash your hands often, especially after changing a diaper; and clean surfaces that come in contact with saliva or urine. A learning in Italy found that pregnant women who were trained in these methods reduced the risk of contracting CMV by six times. A learning in France found that the risk is low.
In the US, patients may not hear this advice from their obstetricians, however. The American College of Obstetricians and Gynecologists does not recommend telling patients about ways to reduce the risk of CMV. According to ACOG, the evidence that behavioral change can make a difference—from just a few studies—is not enough, and the organization sees the challenges of that approach. Recommendations such as not kissing babies and young children can damage “a mother’s ability to bond with her children,” and these hygiene recommendations “may reassure patients” about their risk of CMV, Christopher Zahn, CEO of ACOG, said in a statement. Atlantic Ocean.
The CMV team disagrees. Gail Demmler-Harrison, a pediatric infectious disease physician at Texas Children’s Hospital, said: A group of international CMV experts, including Demmler-Harrison, approved patient studies in a set of consensus opinion in 2017. Devereaux, with the CMV Foundation, organizes it as an elective. It doesn’t have to be “someone says, ‘You can’t understand it;’ I will not share that with you,” he told me. Without knowing about CMV, women cannot decide what type of risk they are comfortable with or what type of hygiene change is too burdensome. He said: “It is your choice whether you do it or not.” “Having a choice is important.”
More about how behavioral changes can affect the future: Karen Fowler, an epidemiologist at the University of Alabama at Birmingham, is enrolling more pregnant women in schools. clinical trials. Only 8 percent of the participants had heard of CMV before joining the study, he says. Patients receive a short CMV session followed by 12 weeks of verbal reminders. Most importantly, he says, “we’re keeping our message simple”: Minimize the sharing of saliva: not eating leftovers, not sharing utensils, and not cleaning your mouth. This simple rule cuts down on the transmission process. Sure, CMV is also shed in urine, tears, and other bodily fluids—but women don’t always put it in their mouths.
Prevention of CMV can be of great interest because once the fetus is infected, the treatment options are not very good. The best antiviral drugs against CMV are not considered safe to use during pregnancy, and some antiviral drugs, although safe, are not as effective. After children are infected, antiviral drugs can help preserve hearing in those with moderate or severe symptoms from CMV, but they cannot reverse brain damage. And it’s not clear how effective antiviruses are for those with only weaknesses. When does the benefit outweigh the risk? “There is a gray area,” says Laura Gibson, a pediatric infectious disease physician at the University of Massachusetts Chan Medical School. For these reasons, the requirements for screening all newborns vary from state to state, even from hospital to hospital. Knowledge can be power—but with a virus as confusing as CMV, knowledge of the disease doesn’t always point to the best decision.
In an ideal world, all of these could be eliminated with the CMV vaccine. But such a vaccine is not difficult despite the great interest. In the US, the Institute of Medicine approved the CMV vaccine very important around the turn of the Millennium, it’s close twelve candidates for vaccination have been or are being studied. All clinical trials completed, however, have failed. “Protection may seem strong in the first month or year, but it wears off,” says Demmler-Harrison. And even vaccines that stimulate the immune system cannot give one the ability to protect against CMV infection completely.
CMV is a difficult virus to vaccinate because it tricks our immune system. “It evolved with people over millions of years,” says Gibson. “It knows how to get around and live with our immune system.” Our immune system is not able to eliminate the virus, which comes out from time to time from our cells to match and try to find another one that causes it. Therefore a vaccine that fully protects against CMV may need to stimulate our immune system to do things it cannot do naturally. It has to be better than our immune system. “As time goes on, I think fewer and fewer people think it’s going to work,” says Gibson. But vaccines do not have to protect against all diseases to be effective. Because primary infection is the most dangerous for unborn babies, vaccination can reduce the risk of congenital CMV.
Who to vaccinate is another difficult question to answer for CMV. We can pass the rubella vaccine from mother to fetus. This has the potential to improve immunity which reduces the spread of CMV, period. But the virus does not cause serious harm to young children, and immunity may decline as they grow to childbearing age. Or we can vaccinate young people, as we do with meningococcal disease, but young people may miss the vaccine and again, the immune system may decline quickly. What about all pregnant women? By the time someone sees a doctor during pregnancy, it may be too late to be protected during the period of greatest risk of CMV, in the first trimester. A better understanding of CMV’s defense and spread can help scientists choose the best strategy. Gibson is conducting research (sponsored by Moderna, which is testing a CMV vaccine) into how the virus spreads and what types of immune responses are associated with shedding.
Until a vaccine is developed—it must be—the only way to prevent CMV infection is the age-old method of avoiding body fluids. It is imperfect. Its actual performance is difficult to quantify. Some people may not find it necessary, because of the low risk of CMV in any pregnancy. There are, after all, already many things to worry about when expecting a child. Is there anyone else? Or, you might think about it, what else is it?
The article incorrectly stated that Robert Pass had died.