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Mythbuster: ‘Covid-19 vaccine might make you infertile and you can’t have it if you’re pregnant or breastfeeding’

Mythbuster: ‘Covid-19 vaccine might make you infertile and you can’t have it if you’re pregnant or breastfeeding’

The reality: It is natural to be concerned about what medicine you take when you are pregnant and it wasn’t until April 2021 that the Joint Committee on Vaccination and Immunisation (JCVI) advised that pregnant women should be offered the vaccination, at the same time as people in their age or risk group.1,2

Covid-19 can be very serious in pregnant women, particularly in the third trimester, and so it is important that all healthcare professionals give a clear and unequivocal message which supports vaccination in pregnancy. The concept of vaccinating in pregnancy isn’t new – we have been giving the flu and pertussis vaccines to pregnant women for years and we routinely vaccinate women who are breastfeeding.  

It is often the case that during drug development, the testing process excludes pregnant women and, therefore, it can be difficult to assert that a new drug is safe. The advice to give the Covid-19 vaccine to pregnant women is based on the following data, available in a decision aid3 which women may want to use:  

  • As of 20 August 20 2021, over 147,000 pregnant women have been vaccinated in the United States, and 55,000 in England and Scotland. There have been no adverse effects recorded.  
  • Studies involving 40,000 women have shown that the vaccine does not increase the risk of miscarriage, stillbirth, congenital abnormalities or having a baby who is small for their gestational age.  
  • The Covid-19 vaccination does not contain any live coronavirus. Therefore, it is impossible for a woman, or her baby, to catch Covid-19 from the vaccine.  
  • Contracting Covid-19 whilst pregnant doubles the risk of prematurity and stillbirth, as well as the risk that the woman will need hospital admission and be severely ill.  
  • More than 99% of women admitted with Covid-19 between February and August 2021 were unvaccinated.  

Pregnant women who are starting their vaccination course should be offered the Pfizer-BioNTech or Moderna vaccines, as these have the most data in this group of women. However, those who have already had a first dose of the AstraZeneca vaccine should have their second dose with the same vaccine, as there is limited information on a ‘mix and match’ approach to the two vaccine doses.  

There is no plausible mechanism by which any ingredient in the vaccine could pass to a baby through breast milk. There is, therefore, no reason for breastfeeding women to avoid the vaccine, or to express and discard their milk for any length of time after being vaccinated.  

Vaccine hesitancy is a significant issue which was highlighted as one of the top ten threats to global health in 20194 and many women are hesitant about getting the Covid-19 vaccine. If a patient of yours is unsure about being vaccinated during pregnancy, point her towards the RCOG decision making aid3 and if she is still unsure then suggest that she discuss it with her midwife or consultant at her next appointment. There are also some helpful videos on the RCOG website, including one aimed at midwives5.  However, it is important to make it clear that a pregnant woman who wants to be vaccinated does not have to wait to have this discussion with a healthcare professional, the best course of action is for her to book the vaccine as soon as possible, which she can do via her GP (in some areas) or via the government website.6 

The other concern which women of childbearing age may express is that the vaccination will make it difficult for them to conceive in the future. These concerns were first expressed in December 2020 after an ex-Pfizer employee wrote to the European Medicines Agency to raise concerns that there is a similarity between a protein involved in placental function (syncitin) and the spike protein of the Covid-19 vaccine. The suggestion was that an antibody response to the spike protein could cause difficulties in conception, or an increased risk of miscarriage, possibly by damage to placental function. However, in reality there is very little similarity between syncitin and the Covid-19 spike protein, so there is no plausible mechanism for a difficulty in future fertility after having been vaccinated against Covid-195.  

The myth about Covid-vaccine and fertility was further boosted by reports of women (probably around 0.5% of those vaccinated6) experiencing changes in their periods after having their vaccine. It is likely that this is a short-term response, similar to that which can cause periods to change during periods of stress and anxiety, and we should be clear to women that it does not represent a threat to their future fertility. Other supporting data includes the fact that in the trials of the Covid-19 vaccine there was no difference in the rate of accidental pregnancy between the group who had the vaccine and the group who had a placebo; if the vaccine caused subfertility, you would expect to see some effect during the trials. Animal studies have also shown no impact of the vaccine upon fertility. The British Fertility Society has a very useful document7 which you may wish to signpost your patients to. It is important that any women with a prolonged change in their bleeding pattern report this to their GP, as there may be a number of courses such as infection or malignancy, which are unrelated to the Covid-19 vaccine.

The Covid-19 vaccination is a life-saving intervention and rates of the disease, hospital admission and deaths have fallen sharply since we started vaccinating. As healthcare professionals we have an obligation to understand the issues that concern our patients and should be well enough informed to be able to give a clear message that vaccination is safe and that any patient who remains unvaccinated is taking a significant risk with their health.  


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Covid-19 can be very serious in pregnant women, particularly in the third trimester, and so it is important that all healthcare professionals give a clear and unequivocal message which supports vaccination in pregnancy.