This sheet is about exposure to tofacitinib 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 tofacitinib? 

Tofacitinib is a medication that has been used to treat rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and ulcerative colitis. Some brand names for tofacitinib are Xeljanz® and Xeljanz XR®. 

MotherToBaby has fact sheets on rheumatoid arthritis here: https://mothertobaby.org/fact-sheets/rheumatoid-arthritis/, psoriasis here: https://mothertobaby.org/fact-sheets/psoriasis-and-pregnancy/, ankylosing spondylitis here: https://mothertobaby.org/fact-sheets/ankylosing-spondylitis/ and inflammatory bowel disease here:  https://mothertobaby.org/fact-sheets/inflammatory-bowel-disease-pregnancy/.  

Tofacitinib has been studied in treating severe COVID-19. Since there is little information about tofacitinib in pregnancy and breastfeeding, it is not currently recommended for treatment of COVID-19 in women who are pregnant or breastfeeding if other recommended treatment options are available. However, the National Institutes of Health (NIH) also states that necessary COVID-19 treatments should not be withheld from women just because they are pregnant or breastfeeding. More information on COVID-19 can be found in our fact sheet here: https://mothertobaby.org/fact-sheets/covid-19/.  

Sometimes when women 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 tofacitinib. Can it make it harder for me to get pregnant?  

It is not known if tofacitinib can make it harder to get pregnant. 

Does taking tofacitinib increase the chance of miscarriage?  

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not been done to see if tofacitinib increases the chance of miscarriage. Reports of tofacitinib use during early pregnancy have not suggested an increased chance of miscarriage. 

Does taking tofacitinib 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 tofacitinib, might increase the chance of birth defects in a pregnancy. 

There are limited studies on the use of tofacitinib in pregnancy. No increased chance of birth defects has been reported when tofacitinib was used during early pregnancy.  

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

Studies have not been done to see if tofacitinib can increase the 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). 

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

Studies have not been done to see if tofacitinib can increase the chance of behavior or learning issues for the child. 

Breastfeeding while taking tofacitinib: 

Tofacitinib has not been well studied for use during breastfeeding. In 2 reports of tofacitinib use while breastfeeding, the amount that was found in breast milk was low. Additionally, no side effects were reported in either breastfed infant. There have been no large research studies on the use of tofacitinib in breastfeeding.  

The product label for tofacitinib and an expert panel recommends women who are breastfeeding not use this medication during breastfeeding, and that breastfeeding should not resume until 18 hours after the last dose. For the extended release form (Xeljanz® XR), they recommend waiting 36 hours after the last dose before breastfeeding again. This is because there is not enough information available on the use of tofacitinib to know if/how it could affect breastfeeding or a breastfed child. But the benefits of using tofacitinib and breastfeeding might outweigh possible risks. Your healthcare providers can talk with you about using tofacitinib and what treatment is best for you. Be sure to talk to your healthcare provider about all your breastfeeding questions. 

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

Studies have not been done to see if tofacitinib could affect male fertility (ability to get make healthy sperm) or increase the chance of birth defects. 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/.  

Please click here for references.  

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

What is vitamin D?

Vitamin D is a nutrient used by the body to grow and to help absorb calcium, which keeps a person’s bones strong. Most people’s bodies can make vitamin D with exposure to ultraviolet (UV) rays from sunlight. Vitamin D is also found in some foods, such as fatty fish (salmon, trout, tuna, and mackerel), egg yolks, cheese, and some milks. Vitamin D is also available as a dietary supplement. Vitamin D deficiency (not having enough vitamin D) can increase the chance of certain health issues. For example, vitamin D deficiency is the most common cause of rickets, a bone disease that causes softening and weakening of the bones.

There are several forms of vitamin D. There are two major forms: vitamin D₂ (ergocalciferol) and vitamin D₃ (cholecalciferol). Vitamin D₂ is mostly human-made and is added to foods. Vitamin D₃ is made in a person’s body and is found in animal products. Both vitamin D₂ and D₃ can be found in supplements or fortified foods.

The Endocrine Society recommends that women who are pregnant get vitamin D through foods, prenatal vitamins, or other supplements. Talk with your healthcare providers about all supplements/vitamins that you take. Have the bottles or photos of the labels with you so that all ingredients and their recommended daily levels can be reviewed. Products that contain herbal supplements are typically not recommended during pregnancy. For more information on herbal products please see our fact sheet at: https://mothertobaby.org/fact-sheets/herbal-products-pregnancy/.

How much vitamin D is needed by women who are pregnant?

The Recommended Dietary Allowance (RDA) is the amount of nutrients people should aim to get each day. The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is not expected to increase health risks for most people in the general population.

	Recommended daily allowance (RDA)		Upper limit (UL)
Pregnant and age 14 to 18 years old	15 mcg / 600 IU	100 mcg / 4,000 IU
Pregnant and age 19 years or older	15 mcg / 600 IU	100 mcg / 4,000 IU

It is not recommended to take more than the RDA in a day unless it has been prescribed by your healthcare provider.

When looking at daily intake, remember to count amounts from foods, drinks, and from supplements. There are resources available online that list amounts of vitamin D typically found in foods, such as the USDA National Nutrient Database for Vitamin D here: https://ods.od.nih.gov/pubs/usdandb/VitaminD-Food.pdf. Labels on supplements will list the amount of vitamin D in the product. Be sure to talk with your healthcare providers about your specific nutritional needs before, during, and after pregnancy.

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

Taking vitamin D at the RDA and staying below the UL is not expected to make it harder to get pregnant. In 1 study, taking vitamin D up to the daily UL was associated with an increased chance to get pregnant among women who have experienced infertility (inability to get pregnant after 1 year of trying).

It is not known if taking more than the UL of vitamin D can make it harder to get pregnant. Low levels of vitamin D have been associated with an increased chance of infertility.

Does taking vitamin D increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. There is mixed information about low levels of vitamin D (blood levels of vitamin D below 50 nmol/L) and a possible increased chance of miscarriage. In 1 study of over 1,600 women that looked at low levels of vitamin D during pregnancy, an increased chance of miscarriage was reported. However, another study among 5,000 women did not find an increased chance of miscarriage with low levels of vitamin D during pregnancy. Another study found that women who had multiple miscarriages had lower blood concentrations of vitamin D compared to those who had not had multiple miscarriages. Because there can be many causes of miscarriage, it is hard to know if a supplement, an underlying medical condition, or other factors are the cause of a miscarriage.

Does taking vitamin D 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. It is not known if high or low levels of vitamin D might affect the chance of birth defects.

In 27 case reports of infants exposed to high levels of vitamin D (blood levels of vitamin D above 125 nmol/L) during pregnancy, there was no reported increase in the chance of birth defects.

Data from two studies with 192 women suggest a link between neural tube defects (birth defects where the spinal cord or brain did not form correctly) and low levels of vitamin D. This is not enough data to know if low levels of vitamin D increase the chance of birth defects.

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

Limited information suggests taking vitamin D within the RDA is not expected to increase the 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).

High levels of vitamin D (blood levels of vitamin D above 125 nmol/L) have not been linked to an increased chance of pregnancy-related problems. There are case reports of an infant having hypercalcemia (high levels of calcium) after being exposed to high levels of vitamin D during pregnancy. However, no increase in hypercalcemia or hypercalciuria (high levels of calcium in the urine) was reported in a clinical trial of vitamin D supplementation of 2000 IU vs 4000 IU during pregnancy.

Having low levels of vitamin D in pregnancy might increase the chance of low birth weight, low infant calcium levels (hypocalcemia), or preeclampsia (high blood pressure and problems with organs, such as the kidneys), which can lead to seizures (called eclampsia). Low levels of vitamin D have been associated with preterm birth with non-white but not white women who are pregnant.

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

No behavioral or learning differences were reported in 27 case reports of children exposed to high levels of vitamin D (blood levels of vitamin D above 125 nmol/L) during pregnancy,

Some studies have suggested that low levels of vitamin D in pregnancy might increase the chance for the child to have attention deficit hyperactive disorder (ADHD), lower language skills, or autism spectrum disorder. However, many factors are involved when a person develops one or more of these conditions. That makes it hard to study these outcomes and most of these studies did not look at other factors such as underlying medical conditions, family history, medications used, or other exposures. Overall, there is not enough evidence to say that low levels of vitamin D in pregnancy increase the chance of ADHD, lower language skills, or autism spectrum disorder.

Breastfeeding while taking vitamin D:

Vitamin D is a normal part of breast milk. Women who are breastfeeding should continue to get the daily recommended amount of vitamin D unless otherwise directed by their healthcare provider. The RDA for breastfeeding is the same as for pregnancy.

	Recommended daily allowance (RDA)		Upper limit (UL)
Breastfeeding and age 14 to 18 years old	15 mcg / 600 IU	100 mcg /4000 IU
Breastfeeding and age 19 years or older	15 mcg/ 600 IU	100 mcg /4000 IU

Women who are breastfeeding should talk to their healthcare provider and their child’s pediatrician about their specific nutritional needs before, during, and after breastfeeding. Be sure to talk to your healthcare provider about all your breastfeeding questions.

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

In one study, men with low levels of vitamin D (blood levels of vitamin D below 50 nmol/L) had lower sperm motility (movement of sperm) than men with sufficient levels of vitamin D. This could affect a man’s fertility (ability to get a woman pregnant). Studies in humans have not been done to see if vitamin D levels increase the chance of birth defects above the background risk. 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/.

Please click here for references.

This sheet is about exposure to methylmercury 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 providers.  

What is methylmercury? 

Methylmercury is an organic form of mercury. Methylmercury is found in water, soil, plants, and animals. Methylmercury is different from elemental mercury, which is found in thermometers and some dental amalgams (tooth fillings). It is also different from inorganic mercury, which can be found in some factory and workplace settings.  

Where does methylmercury come from? 

Methylmercury comes from mercury. Mercury gets into the air from natural sources, like volcanic eruptions and forest fires, and human activities, like coal-burning power plants. When mercury from the air falls into water (oceans, lakes, rivers, streams), the mercury changes into methylmercury. Fish that live in the water can absorb methylmercury through their gills (organs that allow them to breathe underwater) and from the food they eat.  

How are people exposed to methylmercury? 

Most people are exposed to methylmercury from eating fish, shellfish, and marine animals. Almost all fish have some methylmercury. Exposure to small amounts of methylmercury is not likely to cause harm. However, very high exposure can cause poisoning and serious health problems. Methylmercury crosses the placenta and can be found in the fetal blood at levels higher than those in the woman who is pregnant.  

What are the benefits of eating fish during pregnancy? 

Fish is an important part of a healthy diet and is a good food choice for pregnancy. Fish have protein, long chain polyunsaturated fatty acids (such as omega-3 fatty acids), iodine, selenium, and vitamin D. These are all good for your health and the growth and development of a fetus. Some studies have found that women who eat fish during pregnancy have better pregnancy outcomes than those who do not eat fish. A study found that children born to women who ate fish during pregnancy had higher IQ levels. You can get the benefits of fish by choosing fish with low mercury levels.  

Do some fish have more methylmercury than others? Are there fish that I should avoid eating? 

The U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) advise women who could become pregnant, women already pregnant, women who are nursing, and children to avoid eating fish with high levels of methylmercury.  

Fish that are more likely to have high levels of methylmercury are large fish, fish that live for a long time, and fish that eat other fish. The list below has the highest levels of methylmercury and should be avoided during pregnancy and breastfeeding: 

bigeye tuna,	shark
king mackerel	swordfish
marlin	tilefish from the Gulf of Mexico
orange roughy	whale meat and whale blubber (fat)

If I am planning a pregnancy or am already pregnant, what kind of fish can I eat, and how much? 

Women who are pregnant or could become pregnant should follow the FDA and EPA advice for eating fish. The FDA and EPA have created a chart that divides fish into three groups: “Best Choices,” “Good Choices,” and “Choices to Avoid”. You can see the chart here: https://www.fda.gov/food/consumers/advice-about-eating-fish.  

A typical adult serving of fish is 4 ounces, weighed before cooking. The FDA and EPA suggest eating up to 12 ounces (340 grams) of fish a week for women who could become pregnant or who are currently pregnant. This would equal 2 to 3 servings per week from the “Best Choices” list or 1 serving per week from the “Good Choices” list. 

There are different types (species) of tuna. Different types of tuna are listed under each group. For example, canned light tuna (including skipjack) is listed under “Best Choices.” Albacore (white) tuna and yellowfin tuna can have higher mercury levels and are under “Good Choices.” Bigeye tuna is listed as a “Choice to Avoid”. 

Can I eat fish caught by family and friends from local waters? 

Fish caught from local freshwater lakes, rivers, or streams could have high levels of methylmercury or other local pollutants and might not be safe to eat. The EPA and state and local health departments monitor local freshwater. If you eat fish caught by family or friends, check your local agency at https://fishadvisoryonline.epa.gov/Contacts.aspx. If there is no advice listed, eat only 1 serving and no other fish that week. 

Are there concerns about eating raw fish during pregnancy? 

Women who are pregnant should not eat raw fish, such as that found in sushi and sashimi. This is because raw fish can contain bacteria or parasites that could cause serious illness. Please see our fact sheet on eating meats and seafood at https://mothertobaby.org/fact-sheets/eating-raw-undercooked-or-cold-meats-and-seafood/ for more information. Cooking fish can reduce the risk of illness from bacteria and pathogens, but cooking fish does not reduce the levels of methylmercury in the fish. 

What if I ate more than the recommended amount of fish in a week during my pregnancy? 

Eating fish from the “Choices to Avoid” list 1 time or eating more than the recommended amount of fish for 1 week is not likely to increase the chance for health problems for you or pregnancy. If you eat more than the recommended amount of fish for 1 week, you can eat less fish for the next week or so.  

Are there tests that can tell if I have high levels of methylmercury in my body? 

Blood and hair tests can check methylmercury levels in the body. Blood tests work best right after an exposure. Hair tests might be able to detect ongoing (chronic) mercury exposure. However, these tests can be hard to understand. A urine test may not be helpful in testing for methylmercury. Talk with your healthcare provider about your exposure and whether testing is right for you. There is no standard recommendation to test for methylmercury levels before or during pregnancy.  

I was exposed to methylmercury. Can it make it harder for me to get pregnant? 

Some studies suggest that methylmercury exposure might make it harder to get pregnant. This may be more likely at higher levels. 

Does exposure to methylmercury increase the chance of miscarriage? 

Miscarriage is common and can occur in any pregnancy for many different reasons. It is not known if methylmercury can increase the chance of miscarriage. 

Does exposure to methylmercury 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 methylmercury, might increase the chance of birth defects in a pregnancy. 

When a woman follows the FDA guidance for eating fish in pregnancy, an increased chance for birth defects is not expected.  

High levels of methylmercury exposure during pregnancy can increase the chance of birth defects.  In the past, large poisoning events happened in Japan and Iraq. In these events, food was heavily contaminated with methylmercury. Some adults became very sick or died. Babies born after very high exposures had a small head size (microcephaly), underdeveloped brain, and excess fluid in the brain (hydrocephalus), blindness, muscle weakness, and seizures. Some research also suggests that methylmercury exposure during pregnancy may increase the chance of neural tube defects (such as spina bifida) and heart defects.  

Does exposure to methylmercury increase the chance of other pregnancy-related problems? 

Some studies have suggested an increased chance for preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces (2500 grams) at birth) when a woman has high levels of methylmercury in her body. However, other studies did not find an increased chance for these outcomes. This means that it is not known if methylmercury can increase the chance of pregnancy-related problems. 

Does exposure to methylmercury in pregnancy affect future behavior or learning for the child? 

The developing brain is sensitive to methylmercury throughout pregnancy, so high exposure at any time can be concerning. Very high levels of methylmercury in the diet, as seen from past food contamination events, have been shown to increase the chance of having a baby with a small head size, brain damage, developmental delay, intellectual disability, blindness, muscle weakness, and seizures. These high levels of exposure are not typical.  

Most people in the U.S. are not likely to eat enough fish to reach harmful levels of methylmercury. Studies from countries where people eat fish daily and have mercury levels in blood higher than those of people in the U.S. found no differences in children’s development from methylmercury in fish, even in children followed to age 11 years. In fact, a study found that children born to women who ate fish during pregnancy had higher IQ levels. This included women who had somewhat increased levels of mercury; likely because nutrients in fish, such as omega-3 fatty acids, support brain development. When a woman follows FDA advice for eating fish during pregnancy, her child is not likely to have problems with learning or behavior from methylmercury exposure.  

What if I breastfeed my baby? 

Follow the same FDA and EPA guidelines described above to ensure you are not consuming too much methylmercury. Very few studies have been done to evaluate breastfed infants exposed to high levels of methylmercury in breast milk; and the results are not clear. If tests during pregnancy or after delivery show high levels of methylmercury in your system, then you should discuss the safety of breastfeeding with your healthcare provider. Be sure to talk to your healthcare provider about all your breastfeeding questions. 

If a man is exposed to methylmercury, can it affect his fertility or increase the chance of birth defects? 

Some studies have suggested that high levels of mercury might affect male fertility (ability to make healthy sperm) while other studies have not. It is not known if a man’s exposure to methylmercury can increase the chance of birth defects or learning difficulties in their children. In general, exposures that men 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/.                   

Please click here for references.  

This sheet is about exposure to the respiratory syncytial virus (RSV) vaccine Abrysvo® 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 respiratory syncytial virus? 

Respiratory syncytial virus (RSV) is a virus that can cause infection of the respiratory (breathing) tract. RSV spreads easily from person to person through droplets when an infected person coughs or sneezes. It can also spread through direct contact with surfaces that have the virus on them. Most cases of RSV are mild and cause only cold-like symptoms. However, sometimes RSV can cause an infection in the lungs, such as pneumonia. Serious symptoms like fever, severe cough, wheezing, rapid breathing, and cyanosis (blue skin caused by not having enough oxygen in the body) might require hospitalization or the use of a ventilator to help the person breathe. Infants, babies who are born preterm (before 37 weeks), and people with weakened immune systems have a higher chance of developing a severe RSV infection.  

To learn more about RSV, see the MotherToBaby fact sheet on RSV Infection here: https://mothertobaby.org/fact-sheets/respiratory-syncytial-virus-rsv/. 

What is the RSV vaccine?  

The RSV vaccine causes a person to make antibodies against RSV. When the vaccine is given at the recommended time during pregnancy (32-36 weeks), these antibodies can pass to the fetus. It takes about 2 weeks after getting the vaccine during pregnancy for antibodies to fully pass to the fetus. The antibodies help protect the baby from severe RSV infection for about 6 months after they are born.  

The only RSV vaccine approved for use in pregnancy in the United States is called Abrysvo®. Abrysvo® is a protein subunit vaccine. It does not contain a live virus that can cause RSV. Major medical groups including the Centers for Disease Control and Prevention (CDC) recommend the Abrysvo® RSV vaccine for women who are 32-36 weeks pregnant and have not received the RSV vaccine in a previous pregnancy. The vaccine is recommended for use during pregnancy from September to January in most of the United States.  

Women who received an RSV vaccine during any previous pregnancy are not recommended to get an RSV vaccine again in a current pregnancy. Instead, they should talk to their healthcare providers about protecting their babies against RSV with antibodies given directly to the baby after delivery. CDC has information about the maternal RSV vaccine and infant antibodies here: https://www.cdc.gov/rsv/vaccines/protect-infants.html.     

Other RSV vaccines (such as Arexvy® and mResvia®) are not approved for use in pregnancy. If you believe you received one of these vaccines while pregnant, talk with your healthcare provider about the recommendations for protecting your baby from RSV. Experts do not recommend any special monitoring if a woman was given an incorrect RSV vaccine in pregnancy.  

Can getting the RSV vaccine make it harder for me to get pregnant? 

The Abrysvo® RSV vaccine is recommended for women who are already pregnant (32-36 weeks) and for older adults. Studies have not been done to see if getting the RSV vaccine can make it harder to get pregnant. 

I just got the RSV vaccine. How long do I need to wait before I get pregnant? 

The Abrysvo® RSV vaccine is recommended for women who are already pregnant (32-36 weeks) and for older adults. If a woman happens to get an RSV vaccine before pregnancy, there is no recommended waiting period before getting pregnant.  

Does getting the RSV vaccine increase the chance of miscarriage? 

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not been done to see if the Abrysvo® RSV vaccine can increase the chance of miscarriage. The vaccine is recommended for use during the third trimester of pregnancy, which is past the time when a miscarriage can happen.  

Does getting the RSV vaccine 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 the Abrysvo® RSV vaccine, might increase the chance of birth defects in a pregnancy.  

Studies on the Abrysvo® RSV vaccine during pregnancy have not found a higher chance of birth defects. The vaccine is recommended for use during the third trimester of pregnancy, which is past the time when birth defects are most likely to happen. 

Does getting the RSV vaccine in pregnancy increase the chance of other pregnancy-related problems? 

Studies have not found an increased chance of most pregnancy-related problems, such as low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).  

In early studies on the Abrysvo® RSV vaccine given between 24 and 36 weeks of pregnancy, there were slightly more preterm births (birth before 37 weeks) among women who got the vaccine compared to women who did not. However, ongoing studies on the vaccine have not found a higher chance of preterm birth. The recommendation to get the vaccine closer to the end of pregnancy (between 32 and 36 weeks) allows time for antibodies to pass to the baby before delivery but lowers the chance (if there is one) of delivering early from the vaccine, since the vaccine is given closer to full term. 

Some studies have seen a slightly higher chance of problems related to high blood pressure among women who receive the Abrysvo® RSV vaccine in pregnancy compared to women who do not. It is not clear if these problems are related to the vaccine or to other factors. Other studies have not found a higher chance of problems related to high blood pressure. 

Does getting the RSV vaccine in pregnancy affect future behavior or learning for the child? 

Studies have not been done to see if the RSV vaccine can increase the chance of behavior or learning issues for the child.  

Breastfeeding and the RSV vaccine: 

Studies have not been done on the RSV vaccine in women who are breastfeeding. CDC states that protein subunit vaccines like Abrysvo® pose no risk for women who are breastfeeding or their infants (see https://www.cdc.gov/vaccines/hcp/imz-best-practices/special-situations.html#cdc_report_pub_study_section_5-breastfeeding-and-vaccination). Be sure to talk to your healthcare provider about all your breastfeeding questions. 

If a man gets the RSV vaccine, could it affect his fertility or increase the chance of birth defects?  

Studies have not been done to see if the RSV vaccine could affect male fertility (ability to make healthy sperm) or increase the chance of birth defects. 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/. 

Please click here for references. 

This sheet is about exposure to mRNA COVID-19 vaccines 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 COVID-19?

COVID-19 (Coronavirus Disease 2019) is an illness caused by a virus (called SARS-CoV-2). The virus spreads mostly by close person-to-person contact. When an infected person breathes, talks, coughs, or sneezes, the virus can spread to others who are nearby.  

Having a COVID-19 infection while pregnant increases the chance of severe illness and pregnancy complications. Studies have shown that women who are up to date with COVID-19 vaccines in pregnancy are less likely to get very sick or have pregnancy complications from a COVID-19 infection than those who are not up to date. For more information on COVID-19, please see the MotherToBaby fact sheet at https://mothertobaby.org/fact-sheets/covid-19/. 

What is an mRNA COVID-19 vaccine? 

A messenger RNA (mRNA) COVID-19 vaccine gives the cells instructions to help the body make specific proteins. These proteins are needed to make antibodies to protect against the COVID-19 virus. The mRNA COVID-19 vaccines do not contain live virus, and do not cause COVID-19. The mRNA COVID-19 vaccines approved for use in the United States are made by Moderna (Spikevax®, mNEXSPIKE®) and Pfizer-BioNTech (Comirnaty®). While no vaccine is 100% effective at preventing COVID-19, an mRNA vaccine can greatly lower the chance of getting very sick from the virus. 

Medical organizations including the American College of Nurse Midwives (ACNM), the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine (SMFM) recommend that women who are planning a pregnancy, pregnant, or recently pregnant stay up to date with the latest COVID-19 vaccine. An mRNA COVID-19 vaccine can be given at any time in pregnancy.  

For more information on the protein subunit COVID-19 vaccine, please see the MotherToBaby fact sheet at https://mothertobaby.org/fact-sheets/covid-19-protein-subunit-vaccine/.  

Does getting an mRNA COVID-19 vaccine make it harder to get pregnant?

Some women have reported changes in their menstrual cycle (period) after getting an mRNA COVID-19 vaccine, such as having a slightly longer or heavier period or starting their next period sooner than expected. Studies have found that if these changes happen, they are temporary and do not affect fertility (the ability to get pregnant).  

I just got a COVID-19 mRNA vaccine. How long do I need to wait before I get pregnant?

There is no recommendation to wait before trying to get pregnant after getting an mRNA COVID-19 vaccine. 

Does getting an mRNA COVID-19 vaccine increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Multiple studies have found that getting an mRNA COVID-19 vaccine during pregnancy does not increase the chance of miscarriage.  

Does getting an mRNA COVID-19 vaccine increase the chance of birth defects?

Birth defects can happen in any pregnancy for different reasons. Out of all babies born every 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 an mRNA COVID-19 vaccine, might increase the chance of birth defects in pregnancy. Studies have found no increased chance of birth defects when an mRNA COVID-19 vaccine is given during the first trimester of pregnancy (when the many of the fetal organs are developing).  

Fever is a possible side effect of mRNA COVID-19 vaccines. A high fever in the first trimester can increase the chance of certain birth defects. Acetaminophen is usually recommended to reduce fever during pregnancy. For more information about fever and pregnancy, see the MotherToBaby fact sheet about fever/hyperthermia at https://mothertobaby.org/fact-sheets/hyperthermia-pregnancy/.  

Does getting an mRNA COVID-19 vaccine in pregnancy increase the chance of other pregnancy-related problems?

Studies have found no increased chance of pregnancy-related problems such as stillbirth, preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth when an mRNA COVID-19 vaccine is given any time during pregnancy. Studies have found no increased chance of newborn complications (low Apgar scores [a simple test to check a baby’s health shortly after birth]), stay in the neonatal intensive care unit (NICU), or death of newborns when an mRNA COVID-19 vaccine is given any time during pregnancy.  

COVID-19 virus can increase the chance of pregnancy complications, including preterm delivery. Some studies show that the chance for pregnancy complications is lower in vaccinated women compared to unvaccinated women. Studies also show that receiving an mRNA COVID-19 vaccine in pregnancy does not increase the chances of developing gestational diabetes or high blood pressure in pregnancy. 

Does getting an mRNA COVID-19 vaccine in pregnancy affect future behavior or learning for the child?

Based on what is known about how vaccines work in the body, getting an mRNA COVID-19 vaccine is not expected to increase the chances of behavior or learning problems for the child. A study of over 100 infants exposed to mRNA COVID-19 vaccines during pregnancy found no increased chance of developmental delays at 12 months of age.  

Does getting an mRNA COVID-19 vaccine during pregnancy protect the baby from the virus after delivery?

When a woman who is pregnant gets an mRNA COVID-19 vaccine, her body makes antibodies that can pass to the fetus. Research shows that more antibodies are passed through vaccination than through infection. Babies born to vaccinated mothers are better protected from COVID-19 and are less likely to be hospitalized with it after birth. 

Breastfeeding and mRNA COVID-19 vaccines:

Small studies have found that mRNA from a COVID-19 vaccine is unlikely to enter the breast milk. If any small amounts of vaccine ingredients did enter the breast milk, they would most likely be destroyed in the baby’s stomach. About 10% of women have reported changes in milk supply after getting a COVID-19 mRNA vaccine, but their supply returned to normal within a day or two. There is no recommendation to stop or delay breastfeeding or discard breast milk after getting an mRNA COVID-19 vaccine. 

Antibodies against the COVID-19 virus have been found in the breast milk of women who have been vaccinated with mRNA vaccines. Be sure to talk to your healthcare provider about all your breastfeeding questions.  

If a man gets an mRNA COVID-19 vaccine, could it affect his fertility or increase the chance of birth defects?  

Two studies found no differences in the amount of sperm made before and after getting an mRNA COVID-19 vaccine. Other studies of over 200 men found no difference in sperm count and motility (movement) before and after mRNA COVID-19 vaccination or compared to unvaccinated men. 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/. 

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