Considerations for the COVID-19 Virus and Vaccine in Pregnancy and Breastfeeding

Bet you never thought you’d be pregnant during a global pandemic. But here we are, over a year into the COVID-19 pandemic. And now, as a pregnant or postpartum person, you are not only faced with the combined excitement and stress of growing a family, you are faced with some big decisions.

What are the best ways to avoid the virus? What are the risks to you and baby of getting the virus in pregnancy? Should you get the vaccine while pregnant? What about while breastfeeding? Should you allow your unvaccinated family members around a new baby?

These are complex decisions that only you can make. As with any vaccine, there are risks and benefits to consider, including your own health history (including allergies, immune function, and past reactions to vaccines). The risks, as well as potential benefits, may be different during pregnancy and postpartum than for the general adult population. And, there are long-term risks we don’t fully understand about both the disease and the vaccine, as long-term data is not available. 

That being said, we hope that this article summarizing the recent evidence-based information around both the risks of COVID in pregnancy and the known risks and benefits of the COVID-19 vaccine helps empower you in deciding what is uniquely right for you and your baby. 

Note that the research presented around vaccines is primarily on the mRNA vaccines from Moderna and Pfizer-BioNTech, as the Johnson & Johnson vaccine has not been in use as long to gather meaningful data. 

COVID-19 Infection in Pregnancy

Risks

We know there are risks to contracting COVID-19 during pregnancy and studies have attempted to quantify and better understand this risk.

In one cohort study of 252 COVID positive pregnant women and 3,122 COVID negative pregnant women tested in outpatient and inpatient settings at a large county medical center, adverse pregnancy outcomes were similar. Neonatal infection occurred in 3% of infants, predominantly among infants born to asymptomatic or mildly symptomatic women. Placental abnormalities were not associated with disease severity, and the rate of hospitalization of COVID positive pregnant women was similar to rates among nonpregnant women. 

In another study among 598 hospitalized pregnant women with COVID-19, 272 women were symptomatic at hospital admission. Severe illness occurred among symptomatic pregnant women only with 16% admitted to intensive care units, 8% put onto mechanical ventilation, and 1% died. Pregnancy losses occurred in 2% of pregnancies during COVID-19-associated hospitalizations and were experienced by both symptomatic and asymptomatic women. Women hospitalized during the first or second trimester were more frequently symptomatic (84.0%) than those hospitalized during the third trimester (39.9%). The prevalence of preterm delivery among live births during COVID-19–associated hospitalizations was slightly higher (12.6%) than the rate observed in the general U.S. population in 2018 (10.0%). In this study, preterm births occurred approximately three times more frequently in symptomatic pregnant women than in those who were asymptomatic. 

Of course, every case is different and there is still a lot we don’t know about this virus. While some may experience mild and short term effects, others may experience more severe and long-term effects. Long term effects on babies have not been studied as the data simply won’t exist for several years.

Immunity / Antibody transfer

A large study was performed on 1,714 pregnant women who delivered newborns in the northeastern United States during the early stages of the COVID-19 pandemic, from April to August 2020. Investigators collected discarded maternal and cord blood from 1,471 eligible mother-newborn pairs (those who had contracted COVID-19 during pregnancy) to measure antibody concentrations and efficacy of transfer of antibodies from mother to baby (via placenta). This data allowed the researchers to assess the potential for protection of infants in early life.

While only 83 women (6% of the study population) had detectable IgG and/or IgM antibodies at delivery, the majority of infants born to COVID-19 positive mothers (87%) had detectable IgG antibodies at birth. However, infants born to mothers with very low IgG levels did not have antibodies present at birth. The study found that transfer of antibodies to infants occurred regardless of the presence of symptoms in the mother or the severity of disease. In other words, even if a mother presented little to no symptoms during infection, the baby was often born with antibodies. It is unknown how long the antibodies in both mother and baby will remain in the body, but IgG antibodies typically last 4-6 months in infants.

The study found that the time available for antibody transfer is another important factor. The effectiveness of placental transfer of antibodies increased when the time between maternal infection and delivery was longer. In other words, if a mother was infected earlier in her pregnancy, her baby was more likely to be born with antibodies than if she was infected later in her pregnancy.

In short, it is possible for a pregnant woman who was infected by COVID during pregnancy to pass antibodies onto her unborn baby. However, it is unclear how long these antibodies last, and research has shown that antibody levels present in infants induced by natural COVID infection in pregnancy are significantly lower than vaccination-induced antibody levels in infants whose mothers were vaccinated during pregnancy.

COVID-19 Vaccine in Pregnancy

Risks

While there are not any known safety concerns to the COVID vaccine during pregnancy, there is limited data available in general, and none of it is long-term as it is a new vaccine. 

Pregnant women were not specifically included in pre-authorization clinical trials of COVID-19 vaccines, so the best way we have to observe safety is post-authorization safety monitoring and research. One of the primary means we have to do this is through the V-safe vaccine tracking database. As of February 16, 2021, 30,494 pregnant women reported their vaccinations to the V-safe database. The reactogenicity profile and adverse events observed among pregnant women in V-safe did not indicate any safety problems, and most (73%) reports among pregnant women involved non-pregnancy specific adverse events, similar to that of non-pregnant people, like injection site pain. 

The table below summarizes V-safe pregnancy registry outcomes of interest in COVID-19 vaccinated pregnant women as compared to benchmark background rates of the same adverse events. It shows that as of the time of this report, the pregnancy outcomes, complications, and neonatal impacts generally occur at the same frequency as in the population as a whole. The full findings can be found in the presentation at this link, as well as a list of references for the sources of background rate data.



If curious, you can search for adverse reactions to vaccines on the Vaccine Adverse Event Reporting System (VAERS), however, there is currently not a filter for pregnant or lactating women, so it is not possible to compare whether the number of adverse events is substantially different in pregnant or lactating people as compared to the population as a whole. In addition, the events reported to VAERS are self-reported, and there is no confirmation of their accuracy or validity. It is also important to note that for any reported event, no cause-and-effect relationship has been established. 

While this is all very promising data, it is still limited and all short-term. We will not have any research on the long-term effects of the vaccine on mothers or babies for years to come. The mRNA vaccine technology is new, and there is simply no way to ensure safety at this time.

Immunity / Antibody Transfer

A number of studies released in early 2021 have shown that the COVID-19 mRNA vaccines generated robust immunity in pregnant and lactating women, with immunogenicity and reactogenicity similar to that observed in non-pregnant women. The vaccine-induced immune responses were found to be significantly greater than the response to natural COVID-19 infection. In addition, immune transfer to unborn babies occurs via placenta of COVID-specific immunoglobulin G (IgG).

A cohort study of 131 reproductive-age vaccine recipients (84 pregnant, 31 lactating, and 16 non-pregnant) at two academic medical centers evaluated the quantity of antibodies of spike and RBD IgG, IgA (found in the linings of the respiratory tract and digestive system, as well as in saliva, tears, and breast milk) and IgM (found mainly in blood and lymph fluid, the first antibody the body makes when it fights a new infection) were quantified in participant blood (for the 131 pregnant women) and breastmilk (for the 31 lactating women) at baseline, at the time of the second vaccine dose, at 2-6 weeks post second vaccine, and at delivery. The study found that vaccine-induced antibodies were equivalent in pregnant and lactating compared to non-pregnant women and all levels were significantly higher than those induced by a natural COVID infection during pregnancy. Vaccine-generated antibodies were present in all umbilical cord blood and breast milk samples. Antibody levels were lower in umbilical cord compared to maternal blood, although not by a statistically significant amount. The second vaccine dose (boost dose) increased SARS-CoV-2-specific IgG, but not IgA, in maternal blood and breastmilk. No differences were noted in reactogenicity across the groups.

The two mRNA vaccines are very similar, but the study did pick up a difference. Moderna's two-shot regimen appeared to generate more of a certain type of antibody called IgA than Pfizer-BioNTech's.

However, we don’t know how long these antibodies last, nor do we know whether the presence of these antibodies would protect a baby entirely from the virus. The research is new, but it provides a great deal of promise.

It is also important to note that the timing of the vaccine during pregnancy can impact the level of antibodies transferred to the baby. An article in JAMA Pediatrics reported that “the timing of maternal vaccination to protect the infant, as opposed to the mother alone, would necessitate an adequate interval from vaccination to delivery of at least four weeks, while vaccination early in gestation and even late in the third trimester could still be protective for the mother.” 

The study also acknowledges that transplacental transfer of antibodies begins around 17 weeks of gestation and increases exponentially as gestation advances and the placenta grows. Given these facts, the JAMA report suggests that maternal vaccination starting in the early second trimester of gestation might be optimal to achieve the highest levels of antibodies in the newborn. 

COVID-19 Infection while Breastfeeding

Risks

There is certainly a risk that a mother who is actively infected with COVID-19 may pass on the virus to a nursing infant. However, this risk is primarily due to the close proximity of a mother to her infant, as there is no evidence that the virus is transmitted through breast milk

In a study of 101 newborns born to mothers with COVID-19 at a hospital in New York City, only two newborns (2%) tested positive for COVID-19. Neither of these two infants had clinical evidence of infection, despite most infants rooming-in with and direct breastfeeding from mothers. About half (55) of the infants were followed up in the first two weeks of life in a new COVID-19 Newborn Follow-up Clinic, and all had remained healthy.

Given the available evidence on how the virus spreads, the American College of Obstetrics and Gynecology (ACOG) and the World Health Organization (WHO) advises that mothers with COVID-19 continue to breastfeed their babies, but to practice careful hand hygiene and wear a face mask to help minimize the infants’ exposure to the virus. 

Immunity / Antibody Transfer

A small study of 15 lactating women who had recovered from COVID and who were breastfeeding babies at the time found that samples from all women had COVID antibodies, providing promising evidence that breastfeeding mothers could pass viral immunity to their babies. These results confirm findings of a prior small study in the Journal of Perinatology that found different types of COVID antibodies in 58.5% to 97.6% of breast milk samples.

It’s worth noting that the antibodies that tend to be found in the highest concentrations in breast milk are secretory IgA ((s)IgA) antibodies. This type of antibody is secreted by B cells from the mucosal immune system in the mother’s small intestine. B cells travel through the blood to the mammary glands and secrete IgA that’s then shuttled from the mammary tissue to the milk via a transporter protein. Those proteins, called secretory components wrapping around the antibodies and can protect them from being degraded in the infant mouth and gut. While they may be better protected when passed to infants, they may not provide protection as long as other antibodies, like IgG.

Further research will need to be performed to determine how long antibodies passed through breast milk last in infants, and whether they are effective at preventing a COVID infection in an infant.

Ultimately, the evidence we have right now suggests that the benefits of breastfeeding and the potential for antibodies to be spread through breast milk outweigh the risk of potential spread to an infant.

COVID-19 Vaccine while Breastfeeding

Risks

Lactating women were not specifically included in pre-authorization clinical trials of COVID-19 vaccines. However, the Academy of Breastfeeding Medicine made the following statement around vaccine safety during lactation:

During lactation, it is unlikely that the vaccine lipid would enter the bloodstream and reach breast tissue. If it does, it is even less likely that either the intact nanoparticle or mRNA transfer into milk. In the unlikely event that mRNA is present in milk, it would be expected to be digested by the child and would be unlikely to have any biological effects. While there is little plausible risk for the child, there is a biologically plausible benefit. Antibodies and T-cells stimulated by the vaccine may passively transfer into milk and protect the infant from infection with SARS-CoV-2.”

ACOG has made a similar statement and the International Lactation Consultant Association is a good resource for a number of studies and information around the COVID-19 vaccine in lactating women.

It is also important to note that no adverse reactions with respect to milk supply have been officially reported by lactating women who have received the COVID-19 vaccine.

Immunity / Antibody Transfer

Since the Academy of Breastfeeding’s statement was made, we now have evidence that indeed COVID-19 antibodies do transfer to breast milk. We also know that the COVID-19 mRNA vaccines generated robust humoral immunity in lactating women, with immunogenicity and reactogenicity similar to that observed in non-lactating women. 

As mentioned previously, the cohort study of 131 pregnant and lactating women found that vaccine-induced antibodies were equivalent in pregnant and lactating women compared to non-pregnant women and all levels were significantly higher than those induced by a natural COVID infection during pregnancy. Vaccine-generated antibodies were present in all umbilical cord blood and breast milk samples. 

In addition, a study of 84 women (who provided 504 breast milk samples) published on April 12, 2021 in JAMA found a “robust” secretion of SARS-CoV-2 specific immunoglobulin IgA and IgG antibodies for six weeks after vaccination among breastfeeding women. IgA secretion was evident as early as two weeks after the first dose (of the Pfizer-BioNTech vaccine), followed by a spike in IgG after four weeks (one week after the second vaccine). These antibodies found in breast milk showed strong neutralizing effects, suggesting a potential protective effect against infection in the infant. Note that 35% of the infants studied were exclusively breastfed at the time of the study. No mother or infant experienced serious adverse events during the study period. Only mild adverse events were reported in 56% (dose 1) and 62% (dose 2) of women, with local pain and fatigue as the most common complaints. Note that four infants developed a fever during the study period, on day 7,12,15, and 20 after maternal vaccination. All four also had upper-respiratory symptoms. However, the research does not suggest causality between vaccine and fever/upper respiratory symptoms. Rather it is expected to be a result of regular winter cold/flu season. Three of these infant’s symptoms resolved without treatment, one received antibiotics.

Again, the type of antibodies passed through breast milk tend to be different than those passed while in the womb. It is suspected but not confirmed that antibodies passed through the womb may last longer than antibodies passed through breast milk.

It’s worth addressing how breast milk can impact older babies, too. We understand that some breastfeeding mamas who have gotten the COVID vaccine want to provide pumped breast milk to toddlers who have already weaned in hopes that they can pass along the antibodies to their other kids as well. Unfortunately, there isn’t any evidence to show that this is effective. Based on what we know, antibodies passed through breast milk may be effective in helping a toddler through an active infection or helping in the event of an exposure in the days immediately surrounding consumption of breast milk. However, there is simply no evidence to suggest that the secretory IgA antibodies would be able to affect a toddler’s mucous membranes as they do an infant’s, or that they would survive a toddler's more mature digestion and exist long enough to provide lasting protection. That said, there also isn’t evidence to confirm that antibody transfer is completely ineffective for toddlers, and there is little risk to offering a toddler pumped breast milk as long as it isn’t taking supply away from a breastfed infant.

Seek Out Reputable Info

Before we close, we want to address that there is a lot of information out there about the COVID virus and vaccine. Some of it is reputable and trustworthy, some of it is not. Be wary of the source of your information. This is not the time to turn to an unqualified Instagram influencer or unknown source on YouTube for recommendations. Trust only credentialed and cited information that links to trustworthy studies. If you cannot identify the source of a claim, you are smart to question its validity. Ask yourself: 

  • Who is reporting this information? 
  • What are their credentials? 
  • Where are there sources? 
  • Do I trust their sources?

It’s Up to You, Mama

Ultimately you need to weigh your own personal risk of contracting COVID with your comfort level with the vaccine. Nobody can make this decision for you but you. We encourage you to do your own research through trusted medical advisors and evidence-based sources. 

Whether you choose to get the vaccine or not, immune support is a wise choice. Our Prenatal Multi contains safe and supportive doses for mamas and mamas-to-be of many immune-supporting nutrients: 500mg of Vitamin C, 25mg of Zinc, 1500mcg of Vitamin A, and 4,000 IU of Vitamin D.

More than anything, mama, we’re rooting for you during this unprecedented time to be navigating pregnancy and postpartum!