This sheet is about exposure to vaccines in pregnancy and while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.

What are vaccines?

Vaccines help protect you from diseases. Vaccines cause your body’s immune system to make antibodies against bacteria or viruses. Once these antibodies are made, your body has an easier job of stopping you from getting sick if you are exposed to these bacteria or viruses in the future. Most vaccines are given by injection (shot), but some can be taken orally (by mouth) or given with a nasal spray. Vaccines may require multiple doses and periodic boosters to provide the best protection.

What are the different types of vaccines?

A “live” vaccine is made from viruses or bacteria that have been weakened, but not killed. Given the small possibility that a live vaccine might cause the disease itself, live vaccines are not routinely given to women who are pregnant. Some “live” vaccines include the human papillomavirus (HPV) vaccine, measles, mumps, and rubella (MMR) vaccine, varicella (chickenpox) vaccine, live influenza vaccine (nasal flu vaccine), and certain travel vaccines like typhoid fever, and yellow fever.

An “inactivated” vaccine is made from viruses or bacteria that have been killed. An inactivated vaccine cannot cause the disease that it is given to prevent. Many vaccines are in the “inactivated” category including the injected influenza vaccine (flu shot) and the Tdap vaccine.

Other kinds of vaccines, such as messenger RNA (mRNA) and viral vector vaccines, use only certain material from the virus. These vaccines cannot cause the diseases they are given to prevent. Some of the COVID vaccines are in this category.

Are there any vaccines that are recommended in pregnancy?

It is recommended that women who are pregnant receive the seasonal inactivated influenza vaccine (flu shot). Women who are pregnant have a higher chance of developing serious complications from influenza (flu). Getting the seasonal inactivated influenza vaccine (flu shot) is the best way to protect yourself and your baby. You can get the influenza vaccine anytime during your pregnancy. For more information, please see the MotherToBaby fact sheet on the Seasonal Influenza Vaccine (Flu Shot) at https://mothertobaby.org/fact-sheets/seasonal-influenza-vaccine-flu-shot-pregnancy/.

The Tdap vaccine, which protects against whooping cough, is also recommended in pregnancy. You can get the Tdap vaccine anytime during pregnancy; but getting it during the third trimester (between weeks 27-36) may help protect your baby from illness after being born. For more information, please see the MotherToBaby fact sheet on the Tetanus, Diphtheria and Pertussis (Tdap) Vaccine at https://mothertobaby.org/fact-sheets/tetanus-diphtheria-pertussis-tdap-vaccine-pregnancy/.

The American College of Obstetricians and Gynecologists (ACOG), the American Society for Reproductive Medicine, and the Society for Maternal-Fetal Medicine all recommend that women who are pregnant be vaccinated against COVID-19. Women who are pregnant are at increased risk for severe illness and are more likely to have a preterm delivery (before 37 weeks) if they are infected with COVID-19 during pregnancy. For more information, please see the MotherToBaby fact sheets at https://mothertobaby.org/pregnancy-breastfeeding-exposures/covid-19/.

The Centers for Disease Control and Prevention (CDC) recommend the Abrysvo^TM RSV vaccine for women who are 32-36 weeks pregnant during RSV season. In most regions of the continental US, RSV season is from September to January. However, the timing and severity of RSV seasons can be different from year to year. For more information, please see the MotherToBaby fact sheets at https://mothertobaby.org/fact-sheets/respiratory-syncytial-virus-rsv-vaccine-abrysvo/.

The need for other vaccines during pregnancy will vary. Talk to your healthcare providers about the potential risks and benefits of any other vaccines you might need.

Are there any vaccines that should be avoided, if possible, in pregnancy?

Live vaccines are usually not given in pregnancy because of the small possibility that the woman who is pregnant or the developing baby could get the disease from the vaccine. However, if there is a high chance of exposure to an infectious agent that might be dangerous in pregnancy, the benefits of getting a live vaccine might outweigh any risks.

If you require a specific vaccine, contact MotherToBaby for more information. You can also refer to recommendations from the Centers for Disease Control and Prevention (CDC): https://www.cdc.gov/vaccines/pregnancy/index.html.

Is it ok for my child to be vaccinated while I am pregnant?

A child’s vaccine does not increase risk to other people around them, including women who are pregnant. In addition, if you have received the recommended vaccines during your lifetime, you are highly protected from becoming infected by others.

Can vaccines make it harder for me to become pregnant?

Limited studies on this question have not shown that vaccines would make it harder to become pregnant.

Do vaccines increase the chance of miscarriage?

Miscarriage can occur in any pregnancy. Many studies have not shown an increased chance of miscarriage.

Do vaccines increase the chance of birth defects?

Every pregnancy starts out with a 3-5% chance of having a baby with a birth defect. This is called the background risk. Studies on vaccines in pregnancy have not shown an increased chance of any pattern of birth defects.

Do vaccines increase the chance of other pregnancy complications?

Studies on vaccines have not shown that they cause pregnancy complications.

Does getting vaccines cause long-term problems in behavior or learning for the baby?

Based on the studies reviewed, vaccination during pregnancy is not expected to cause behavioral or learning issues for the baby.

What about thimerosal in vaccines?

Thimerosal is a preservative. It is found in very small amounts in some vaccines to help stop the growth of harmful bacteria in the vaccine. Large studies have not found thimerosal to cause any harmful effects. Women who are pregnant can receive vaccines containing thimerosal. The CDC answers questions about thimerosal here: https://www.cdc.gov/vaccine-safety/about/thimerosal.html.

Breastfeeding and getting a vaccine:

Studies have shown that most live and inactivated vaccines that are routinely given in the United States and Canada are not harmful during breastfeeding. Smallpox and yellow fever vaccines should not be given to a woman who is breastfeeding unless travel to certain countries is unavoidable and your healthcare provider determines that the benefits of the vaccine outweigh the risks. Be sure to talk to your healthcare provider about all your breastfeeding questions. You can also refer to recommendations from the CDC: https://www.cdc.gov/breastfeeding/breastfeeding-special-circumstances/vaccinations-medications-drugs/vaccinations.html.

If a man receives a vaccine, could it affect fertility (ability to get a woman pregnant) or increase the chance of birth defects in a woman’s pregnancy?

There is no evidence to suggest that vaccines affect the sperm or are transmitted to the developing baby through the semen. In general, exposures to fathers or sperm donors are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.

MotherToBaby is currently conducting a study to learn more about the Tdap vaccine in pregnancy. If you are pregnant and have received the Tdap vaccine or plan to do so, and you are interested in learning more about this study, please contact MotherToBaby Pregnancy Studies at 877-311-8972 or visit https://mothertobaby.org/join-study/. 

Please click here for references.  

This sheet is about exposure to ustekinumab in pregnancy and while breastfeeding. This information is based on published research studies. It should not take the place of medical care and advice from your healthcare provider. 

What is ustekinumab? 

Ustekinumab is a medication that has been used to treat moderate to severe psoriasis, Crohn’s disease, and active psoriatic arthritis. The brand name of ustekinumab is Stelara®.  

MotherToBaby has fact sheets on psoriasis and psoriatic arthritis https://mothertobaby.org/fact-sheets/psoriasis-and-pregnancy/ and Crohn’s disease https://mothertobaby.org/fact-sheets/inflammatory-bowel-disease-pregnancy/. 

 Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take your medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy. 

I take ustekinumab. Can it make it harder for me to get pregnant? 

Studies have not been done to see if taking ustekinumab can make it harder to get pregnant .  

Does taking ustekinumab increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies of over 3000 pregnancies did not find an increased chance of miscarriage when ustekinumab was used during pregnancy.  

Does taking ustekinumab increase the chance of birth defects? 

Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like ustekinumab, might increase the chance of birth defects in a pregnancy. Studies of over 2,500 pregnancies found no increased chance of birth defects when ustekinumab was used during pregnancy.  

Does taking ustekinumab in pregnancy increase the chance of other pregnancy-related problems?

Studies of over 2000 pregnancies found no increased chance of pregnancy-related problems such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth) when ustekinumab was used during pregnancy.  

Can my baby receive live vaccines before one year of age if I take ustekinumab later in pregnancy? 

Ustekinumab can weaken the immune system of the person taking it, so there’s a theoretical (not proven) concern it might also weaken a baby’s immune system if they are exposed during pregnancy. Live vaccines, which contain a small amount of live virus, can cause an infection in people with weak immune systems. Inactivated vaccines, which do not contain live virus, cannot cause an infection with the disease they protect from. In the U.S., the rotavirus vaccine is the only live vaccine routinely given in a baby’s first year.  

Studies of babies exposed to ustekinumab during pregnancy who got the rotavirus vaccine in the first 4 months of life found no higher risk of infections or health problems. There are also reports of babies who were exposed to ustekinumab during pregnancy and received the measles, mumps, and rubella (MMR) vaccine or the varicella vaccine without any health issues.  

Talk with your child’s healthcare provider about your exposure to ustekinumab during pregnancy. They can talk with you about the vaccines your child should receive and the best time for your child to receive them. 

Does taking ustekinumab in pregnancy affect future behavior or learning for the child?  

Four studies of 122 children exposed to ustekinumab during pregnancy showed no increased chance of behavior or learning issues at around 12 months of age. 

Breastfeeding while taking ustekinumab:

Ustekinumab has not been well studied during breastfeeding. Because ustekinumab is a very large protein, it is thought that very little medication would pass into breast milk. Ustekinumab is also a medication that is not well absorbed by the GI tract (gut), so any of the medication that gets into breast milk would be unlikely to enter the baby’s system. Be sure to talk to your healthcare provider about all your breastfeeding questions. 

If a man takes ustekinumab, could it affect fertility or increase the chance of birth defects?

A small study of 12 men exposed to ustekinumab reported no effect of on fertility (ability to get a partner pregnant). Larger studies of over 200 men exposed to ustekinumab and similar medications showed no increased chances of birth defects or miscarriages. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.

MotherToBaby is currently conducting a study looking at autoimmune diseases like psoriasis and the medications used to treat autoimmune diseases in pregnancy. If you are interested in taking part in this study, please call 1-877-311-8972 or visit https://mothertobaby.org/join-study.

Please click here for references.

Lately, it seems like every few months a new infectious disease makes the headlines. The COVID-19 pandemic dominated the news cycle for some time, but as more and more people get vaccinated and the number of severe cases starts to decrease, the media’s focus has shifted to other known or emerging threats. From the flu and respiratory syncytial virus (RSV), to mpox and syphilis, infections seem to be spreading like wildfire. Most recently, measles has made yet another comeback, prompting many women who are planning pregnancy, currently pregnant, or breastfeeding to make sure they are taking steps to avoid infection.

When I logged into our live chat service at www.mothertobaby.org on Tuesday morning, a chat from Alyssa popped up right away. “I’m currently 18 weeks pregnant and there was a measles case reported at my son’s preschool. Do I need to be worried?”

It’s understandable that Alyssa would be concerned. Measles (also known as rubeola) is a highly contagious respiratory disease caused by a virus. According to the Centers for Disease Control and Prevention (CDC) the measles virus can live for up to two hours in an airspace where the infected person coughed or sneezed. If people breathe the contaminated air or touch the infected surface, then touch their eyes, nose, or mouth, they can become infected. Measles is so contagious that if one person has it, up to 90% of the people close to that person who are not immune will also become infected.

Symptoms of measles generally appear about 7-14 days after a person is infected, and can include high fever, dry cough, runny nose, red watery eyes, and a rash all over the body. To date, studies have not identified an increased risk for birth defects when pregnant women get infected with measles during pregnancy. However, research suggests that a measles infection can be associated with an increased risk for miscarriage, premature delivery (having the baby before 37 weeks), and stillbirth.

The first question I asked Alyssa on chat was if she had ever received the Measles, Mumps, and Rubella (MMR) vaccine. Just one dose is about 93% effective at preventing measles, while two doses is close to 97% effective, so it’s the best way to prevent this disease. These vaccines are routinely given in childhood, so Alyssa couldn’t remember if she had received both, but after texting her mom she was able to confirm that she was fully vaccinated. Whew, that was good news. Next we discussed the date of exposure. I asked Alyssa when the positive case was reported at daycare, to which she answered that it was about two weeks ago. More good news. Since neither Alyssa nor her son had experienced any symptoms yet, infection was unlikely.

Since measles doesn’t seem to be going away anytime soon, knowing how to best protect yourself against the illness at all reproductive life stages is important.

Pre-Conception: Women who are planning a pregnancy in the future should make sure they are up to date with their MMR vaccines BEFORE they get pregnant. If you can’t find your vaccine record, call your healthcare provider who may know. If they don’t have a record, a blood test (titer) can be done to determine if you have immunity to measles. If it turns out you are not immune, you’ll want to get two doses of MMR vaccine for optimal protection. Just make sure you wait at least one month after getting the last shot before attempting to get pregnant.

Pregnancy: Since pregnant women shouldn’t receive live vaccines (like MMR), the best thing you can focus on during pregnancy is prevention. Good hand washing is always a good idea. If there is a confirmed measles outbreak near you, consider avoiding crowded public places and steer clear of any locations that have been identified as a known risk.

Breastfeeding: Once you are no longer pregnant, the MMR vaccine can be administered. The CDC considers the MMR vaccine compatible with breastfeeding and side effects for the breastfed baby are not expected.

If you have any questions about measles infection or the MMR vaccine while planning a pregnancy, during pregnancy or while breastfeeding, MotherToBaby is here to help. Give us a call at 866-626-6847, text, or chat with one of our information specialists today.

By MotherToBaby and experts from the Centers for Disease Control and Prevention (CDC)

At 16 weeks pregnant, Maria is busy planning a summer trip for her family. But lately, every time she opens her phone, she sees another headline about measles outbreaks.

It makes her pause and wonder: What does this mean for me and my baby?

What is measles, and why are people worried about it?

Measles is a highly contagious virus that spreads through the air when someone who is sick with measles coughs or sneezes. Since measles spreads so easily, up to nine out of 10 unvaccinated people who come into close contact with someone who has measles will become infected.

Symptoms often include high fever, cough, runny nose, red eyes, and rash. Measles can lead to serious health complications and severe illness. During 2025, about 1 in 10 people with measles were hospitalized.

In recent years, the United States has seen a rise in measles cases. In the past, measles has mostly affected children, but there are also recent increases among people of reproductive age. In 2025, nearly a third of measles cases (1 out of 3) were in adults 20 years of age or older. So far in 2026, nearly a quarter of measles cases (1 out of 4) have occurred in adults. This trend is one reason Maria may feel especially worried.

Why is measles infection concerning during pregnancy?

When you are pregnant, your body changes in many ways. These changes can increase your chances of getting sick from infections during pregnancy.

For example, if you are pregnant and get measles, you have a higher chance of:

• Being hospitalized
• Developing pneumonia
• Rarely, death

Measles during pregnancy can also increase the chance of health problems for the baby, such as:

• Pregnancy loss (including miscarriage or stillbirth)
• Preterm birth
• Low birthweight

Measles can also pass from mother to baby if an infection happens during pregnancy. This can cause serious illness in newborns, hearing loss, and—very rarely—a fatal brain condition called subacute sclerosing panencephalitis, or SSPE, years later.

Even after birth, measles can be dangerous for babies who are too young to get vaccinated against measles.

How can I protect myself and my baby from measles?

This was Maria’s main question as she started planning her trip. When she talked with her healthcare team, she learned that the MMR (measles-mumps-rubella) vaccine is the best protection against measles. Luckily, Maria had received this vaccine when she was younger. 

If you are not up to date with vaccinations, the ideal time to get the MMR vaccine is at least one month before becoming pregnant. The MMR vaccine is not recommended during pregnancy. However, it can be given after delivery, even while breastfeeding.

If you are not sure whether you have immunity against measles, talk with your healthcare provider. MotherToBaby has a tool to help you start the conversation.  While it is important to weigh the risks and benefits of any vaccine with your healthcare provider, serious reactions from MMR vaccination are rare.

After delivery, when you start taking your baby to their well-child visits, talk with your baby’s healthcare provider about the MMR vaccine and ask any questions you may have. Starting conversations early can help you feel confident when it is time for your baby to get vaccinated.

What should I do if I am planning to travel soon or live in an area with a current measles outbreak?

This was also a key question on Maria’s mind. She brought it up with her healthcare provider, and together they talked about her vaccination status as well the status of others in her household. They also looked up the measles activity at her summer trip location and talked about watching for symptoms of measles for 21 days after travel. If you are pregnant, these are helpful steps to take.

If a measles outbreak is happening near where you live, follow local recommendations. Consider avoiding crowded public settings and avoid contact with people who are sick. Encourage people around you (partners, family members, caregivers) to be up to date on MMR vaccination to help protect you and your baby.

What should I do if I am exposed to measles while pregnant?

If Maria is exposed to measles during her trip, her first step would be to call her healthcare provider’s office right away. They can tell her what to do next and how to get into the office safely, if needed, to avoid exposing others.

For pregnant patients who are not immune to measles or do not know if they are immune, they could be given antibodies called immune globulin (IG) after a measles exposure. If you have measles during pregnancy, talk to your baby’s healthcare provider about IG, which might also be recommended for your newborn.

What if I develop symptoms of measles while pregnant?

If you develop a fever and rash, especially if you live in an area with measles or have recently traveled, call your healthcare provider right away, and they can provide further instructions. Be sure to tell them if you have received the MMR vaccine before and where you have traveled.

A few key points:

• Fever in early pregnancy can pose risks, especially if it lasts for a long period of time. Talk with your healthcare provider about how best to treat your fever with fever-reducing medications.
• Taking extra Vitamin A is not recommended during pregnancy because high doses can increase the chance of certain birth defects.

What should I know if I am breastfeeding?

Measles is not spread through breast milk, and infants can receive breast milk from a mother with measles infection. Follow guidance from your healthcare team on precautions, which may include staying away from nonvaccinated people, expressing breast milk, and having a person who is not sick feed your infant your breast milk. Or, they may recommend you wear a mask and practice careful hygiene when breastfeeding and caring for your newborn.

If you are pregnant or breastfeeding and unsure about your immunity to measles or worried about exposure, you are not the only one with these questions. As with Maria, your healthcare provider and MotherToBaby are here to help answer any questions you may have.

References

1. Joseph, NT. Measles in Pregnancy: Clinical Considerations and Challenges. Obstetrics & Gynecology 147(1):p 44-53, January 2026. | DOI: 10.1097/AOG.0000000000006126:
2. Rasmussen, SA; Jamieson, DJ. What Obstetric Health Care Providers Need to Know About Measles and Pregnancy. Obstetrics & Gynecology 126(1):p 163-170, July 2015. | DOI: 10.1097/AOG.0000000000000903
3. Congera P et al. Measles in pregnant women: A systematic review of clinical outcomes and a meta-analysis of antibodies seroprevalence. Journal of Infection 80(2):p152-160, February 2020. | DOI: 10.1016/j.jinf.2019.12.012

Disclaimer: The contents of this post are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention. Reference to any third party, company, or product is intended for factual information only and does not indicate any form of endorsement or approval from CDC, or the U.S. Department of Health and Human Services.

Having measles during pregnancy can increase the chance of serious problems for mom and baby – but can pregnant women receive the measles vaccine? The Measles Protection Decision Tree is an easy-to-use resource designed to help individuals determine if they are protected against measles and understand what steps to take if they need to get an MMR (measles, mumps, and rubella) vaccine. The decision tree provides specific guidance for women who are planning pregnancy, pregnant, postpartum, or breastfeeding. It walks users through checking their vaccine records, reviewing the number of MMR vaccine doses they need, and understanding when to get vaccinated if needed. This resource is provided by MotherToBaby in collaboration with the Society for Maternal-Fetal Medicine.

If you have further questions about measles or the MMR vaccine, contact a MotherToBaby specialist.