RSV (Respiratory Syncytial Virus): Symptoms, Causes, Diagnosis, Treatment
Can RSV Harm A Fetus During Pregnancy? What To Know
During the recent winter months cases of RSV rose quickly. Pregnant people may be particularly concerned about this rise in cases, and whether or not contracting RSV could impact their pregnancy.
Several vaccines are recommended during pregnancy to protect the pregnant person and developing fetus against severe illness.
The Center for Disease Control and Prevention (CDC) recommends the Tdap vaccine to protect against whooping cough, while COVID-19 and flu vaccines may help lower the risk of acute respiratory infection.
Pregnant people are also advised to receive the maternal RSV vaccine Abrysvo during the third trimester to protect their newborn against severe respiratory infection during the first few months of life.
Respiratory syncytial virus (RSV) is a common respiratory illness that may cause mild cold-like symptoms. While most people recover from RSV within a week or two, some people in high-risk groups, such as older adults, young children, and pregnant people, may experience complications from the virus.
Though rare, RSV infection during pregnancy could potentially pass to the fetus through the placenta. Here's what you need to know.
The prevalence of pregnant people who contract RSV is not well established.
Dr. Maris K. Toland, an OB-GYN at Dartmouth Hitchcock Clinics in Bedford, NH, a part of Dartmouth Health, told Healthline that some research estimates between 10–13% of pregnant people may contract the virus.
Toland said that if a pregnant person contracts RSV, antibodies could potentially "pass trans-placentally to the fetus" and reduce the risk of RSV in infants once they're born.
"It is [also] possible for vertical transmission of RSV infection through the placenta to the fetus potentially leading to poor outcomes, such as preterm birth or neonatal respiratory distress after birth," she noted.
Indeed, a 2022 research review found that babies exposed to RSV during pregnancy had breathing difficulties after they were born. No miscarriages resulting from exposure to the virus were reported.
However, such complications are rare, especially among pregnant people who get immunized against the virus.
Dr. Patricia Faraz, board-certified OB-GYN at The Women's Hospital at MemorialCare Saddleback Medical Center in Laguna Hills, CA," told Healthline that in most cases, RSV is "not typically harmful to the fetus."
"The reason to give RSV vaccines to pregnant women is so that the antibodies produced after receiving the vaccine cross the placenta and offer protection to the newborn and infancy period (6 months)," she explained.
"RSV infection in the mother is usually mild and self-limited. It's rare to see severe infection in mothers."
Toland agreed and noted that RSV infections are not usually serious in young, otherwise healthy adults.
In young children and older adults, however, Toland said RSV may cause "dangerous respiratory tract infections [and] can sometimes lead to pneumonia or hospitalization, particularly in people with pre-existing conditions like asthma or other lung conditions."
RSV season runs from October to April in the northern hemisphere, but health experts recommend the maternal RSV vaccine year-round regardless of whether a person has previously contracted the virus.
The RSV shot is administered to pregnant people between 32–36 weeks gestation to protect newborns during the first 6 months of life. Another immunization, Beyfotus (nirsevimab), is a monoclonal antibody treatment given to newborns up to 8 months. It is not an RSV vaccine.
"Up to 80,000 infants can be infected with RSV yearly, requiring hospitalization," Faraz said. "100–300 children will die each year from RSV," she added, highlighting the importance of vaccinating against this respiratory virus.
As with any vaccine, however, the maternal RSV vaccine does not guarantee full protection for a pregnant person or infant once they're born; it only protects against severe illness.
"[Abrysvo] does substantially reduce the risk of severe lower respiratory infection in the infant by 70–90%," Faraz noted.
Toland added that Abrysvo may reduce an infant's risk of being hospitalized from RSV infection by 57% in the first 6 months after birth.
Similar to vaccines that offer protection against respiratory illnesses like COVID-19 and the flu, the maternal RSV vaccine protects against severe illness — but that doesn't always mean you won't catch the virus.
RSV is spread through air droplets or direct contact with people who have the virus. You can reduce your risk of exposure with proper handwashing and wearing a mask for an added layer of protection.
As an extra precaution during pregnancy, you may also wish to avoid or limit contact with people exhibiting potential RSV symptoms resembling a mild cold, such as:
If a pregnant person contracts RSV, it is unlikely the virus will cause harm to a developing fetus or to a newborn infant after birth.
Some research, however, has shown a heightened risk of low birth weight and respiratory distress among newborns exposed to RSV in utero, but these complications are rare.
The CDC and other health experts recommend vaccinating against RSV during pregnancy to protect the mother and child against severe respiratory infection from the virus.
Only one RSV vaccine, Abrysvo, is approved for use in pregnant people during the third trimester.
How Effective Is The RSV Vaccine During Pregnancy And How Does It Work?
Respiratory syncytial virus (RSV) is a respiratory virus causing infection in the lungs, nose, and throat.
RSV affects all ages — including young infants — and infects about 64 million people globally each year.
While RSV symptoms normally feel just like those of the common cold in adults and older children, it can be a much more serious disease in older adults, young children, and babies.
Researchers report that RSV is the most common cause of hospitalization of infants in high-income countries.
The respiratory infection is responsible for about 3.6 million lower respiratory tract hospitalizations in young children each year, with 1.4 million of those in children ages 0 to 6 months.
For this reason, the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) both recommend pregnant people receive an RSV vaccine to help immunize their babies from the disease before birth.
Of the two RSV vaccines currently available, only one vaccine — Pfizer's Abrysvo — is approved by the Food and Drug Administration (FDA) and European Commission for use in pregnant people.
The American College of Obstetricians and Gynecologists recommends the Abrysvo vaccine for people who are 32 to 36 weeks pregnant during the peak RSV season, which is from September to January in the U.S.
"A pregnant woman who receives (the) RSV vaccine in the last trimester — weeks 32 to 36 — will develop antibodies against RSV that will be passed to the fetus and protect the infant against RSV," Dr. Edward Liu, chief of infectious diseases at Hackensack Meridian Jersey Shore University Medical Center in New Jersey explained to Medical News Today.
"Some infants are more susceptible to develop severe RSV symptoms that can lead to hospitalization, requiring oxygen and/or mechanical ventilation to help them breathe," added Chanique Ecby, clinical assistant professor at the University of Houston Andy and Barbara Gessner College of Nursing. "Due to infants being so vulnerable, Abrysvo, the RSV vaccine for pregnant women, should be given to help provide antibodies that will protect the newborn against severe RSV disease after birth."
The Abrysvo vaccine prevents lower respiratory tract disease and severe lower respiratory tract disease caused by RSV in infants from birth through 6 months of age.
Babies are protected by RSV at birth if the pregnant individual received the vaccine at least two weeks prior.
Dr. Sherry Ross, a board-certified OB/GYN and women's health expert at Providence Saint John's Health Center in Santa Monica, CA, spoke with MNT about RSV vaccine's effectiveness:
"The effectiveness of the RSV vaccine in protecting a baby may vary depending on when the vaccine was given to the pregnant woman and the underlying health and lung conditions of the baby."
In a study published in April 2023 of 3,500 pregnant individuals who received Abrysvo, the vaccine helped reduce the risk of severe lower respiratory tract disease by 81.8% within 90 days after birth and 69.4% within 180 days after birth, compared to those who received a placebo.
Additionally, in a subgroup of pregnant individuals receiving the vaccine during 32 to 36 weeks of pregnancy, lower respiratory tract disease risk was lowered by 34.7%, and severe lower respiratory tract disease risk was reduced by 91.1% within 90 days after birth when compared to those who received the placebo.
Dr. Patricia Faraz, a board-certified OB/GYN at The Women's Hospital at MemorialCare Saddleback Medical Center in Laguna Hills, CA, told MNT the advantage of taking the vaccine during pregnancy allows a baby to be born with immunity and immediate protection, as long as the mom received a vaccine for greater than 14 days before the baby is born.
"Basically by giving it to the mom, you're reducing one less vaccine that the baby needs to receive, and they have immediate immunity at birth," Dr. Faraz added.
The FDA's approval of Abrysvo for pregnant people was based on the results of a phase 3 clinical trial evaluating the vaccine's safety and effectiveness.
"Potential side effects from the RSV vaccine are common and similar to other vaccines including injection site discomfort, headache, muscle pain, and nausea," Dr. Ross explained. "There are no side effects to the unborn baby."
Dr. Faraz noted that so far, pregnant people under her care receiving the vaccine have only experienced minimal side effects:
"The most common side effects would be pain or soreness at the injection site, and then other common side effects that have been reported are headaches, nausea, and muscle pain. Honestly, within my group of patients, I haven't heard anybody complain about anything yet — so far it's been well tolerated."
There may be some instances in which a pregnant individual would not be able to receive the RSV vaccine.
For example, according to the CDC, the RSV vaccine should not be given to pregnant people who are less than 32 weeks pregnant. The FDA has this stipulation marked as a warning on the prescribing information for Abrysvo.
"Early in the pregnancy before week 32, (the) RSV vaccine is not recommended as there are reports of preterm delivery," Dr. Liu explained.
"A pregnant woman may be unable to receive the RSV vaccine … if she has a history of severe allergic reaction to any component of the vaccine," Ecby added.
If a pregnant person is unable to get the RSV vaccine during pregnancy, Dr. Ross said the individual would be a perfect candidate to receive nirservimab, which gives RSV antibodies directly to the baby after birth to protect against RSV infections:
"Nirsevimab gives RSV antibodies directly to the baby after birth, adding longer protection than the 6 months that the RSV vaccine affords a newborn. One disadvantage of nirsevimab is it may be harder to get, especially during the high-risk seasons of fall and winter."
Dr. Faraz said monoclonal antibodies can also be given to babies if they are born earlier than the two weeks needed for the vaccine to provide immunity:
"In a case where the baby was born, like let's say a week after the mom was given the vaccine, that baby may still be a candidate to receive monoclonal antibodies after birth. This is (also) an option if you have a baby who was born with a cardiac defect. Even if the mom has been vaccinated, you could still administer the antibodies to the baby for added protection or a baby that severely immunocompromised."
Overall, all medical experts MNT spoke with agree that if a pregnant individual is able to take the RSV vaccine, they should.
"RSV is an infection that for years we know is a risk to small babies and infants," Dr. Faraz said. "Their immunity is weak and RSV is … super common, especially when there are multiple children in the household — it's just going to be so easy for that baby to get exposed."
"Getting the RSV vaccine, between 32 and 36 weeks of pregnancy, is another way to ensure healthcare providers and pregnant women have done everything to give a baby the healthiest start in life, right out of the gate," Dr. Ross added.
"There are no protective vaccines against RSV for babies as their immune systems are not mature," Dr. Liu commented. "RSV seasons are unpredictable and can be severe regionally. RSV can be a serious infection for babies and taking the RSV vaccine can protect the baby."
"If you meet the criteria for the vaccine, give your unborn child a fighting chance to be healthy during RSV season," Dr. Ecby concluded.
38 Weeks Pregnant - What To Expect
Watch our video to see what your baby looks like this weekRemember that wax (vernix) and hair (lanugo) that used to cover your baby's skin? Both are pretty much gone now, shed into the amniotic fluid – that your baby swallows bits of. This partly explains why your baby's very first poo (called 'meconium') is going to be particularly sticky and thick.
And here's a 3D scan of a 38 week baby... So what's happening to your body this week?It's been 38 long, long weeks and, frankly, you've probably had enough of this whole pregnancy thing by now.
You feel huge and heavy and about as nimble as a hogtied hippo. Everything aches or itches or rubs, and it's all just a mighty pain in the piles.
Oh, and if one more person comments about the size of your bump, you might just flatten them with a well-aimed bellyflop. We so know how you feel! And we kind of think it's nature's way of preparing you for labour: if you feel like this, anything's got to be better than being pregnant, right?
In the meantime, we recommend moaning – a lot. A late-pregnancy trouble shared is not exactly a late-pregnancy trouble halved – but it certainly helps!
More like this Our MFMer's 38-week bump of the week
Are you taking pics of your changing bump in these late stages? Check out other MFMers' belfies in our 38 week bump gallery.
Did you know? Your baby's now the length of... 2 loaves of sliced whiteThis week, your baby measures around 49.8cm - the same as two loaves of bread!
And is around the weight of... An empty lightweight suitcaseYour baby now weighs around 7lb (3.2kg)!
4 things you might need to know this week MFMers' tip of the week from our forum"The "palpable" or "engaged" thing on your antenatal notes is so confusing! It's basically a measure, in finger-width 'fifths', of how far down your baby's head is into your pelvis: palpable means what the midwife can feel, and engaged means what she can't. So 2/5ths palpable is the same as 3/5ths engaged" - Charbar15
Want to share your pregnancy with others going through the same as you? There's a birth club for your due date - take a look...
Got yourself some breastfeeding goodies yet?Leaking colostrum through your bra and onto a favourite silky blouse (or even a meh cotton one) can really upset you once you've had your baby - so splash out on some absorbent nipple pads now, while you've still got the wherewithall.
Same goes for cream to keep your nipples supple and hydrated (ooh, doesn't that sound fun) and don't forget to pick up a breastfeeding cover (sometimes called a nursing cover) so you can keep your breastfeeding fashionably under wraps.
Our preg recipe for week 38 - Fruit and nut yoghurt Why sunflower seeds are great for your babyThey're such teeny-tiny things, yet sunflower seeds still manage to pack in protein, vitamins A, B, D, E and K, folic acid, magnesium, calcium, iron, potassium and zinc.
They also contain tryptophan, which can increase production of serotonin, a brain chemical that can calm your mind and boost your mood. Handy when you're irritably hoiking a hot, heavy bump around all day.
See the full recipe and get cooking...
Baby namer - what do you think of these unusual names?Unsure about choosing a traditional name? Looking for something more exotic? What do you think of these names inspired by the natural world?
AzuraAzura is a Persian name that describes the blue of the sky on a clear summer's day.Celeb baby-name-check: Alesha Dixon named her first daughter Azura.
LevonLevon is the Armenian form of Leon - that means lion in Greek. Pronounced Lee-von, it's also the name of a famous 1970s Elton John song (look it up on YouTube, it's pretty epic).Celeb baby-name-check: Uma Thurman named her first son Levon.
If you're in need of more inspiration, check out our Baby Names section for lots more ideas.
So that's plenty for this week, want to take a peek at what lies ahead - or look back at last week?
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