More studies are needed about COVID-19 and pregnancy. 


One question that many couples ask is whether vaccination against COVID-19 could in any way affect a woman and her embryos or fetuses if she becomes or is pregnant. Because of this, several issues may be raised that we shall discuss in the form of questions:

1. Could vaccination against COVID-19 be harmful to pregnant women?

Until more data are available from clinical trials or medical studies in addition to those already conducted, we can say that, at present, there is very little information on whether vaccinating pregnant women might have negative effects on them (12310).

To try to obtain such data, the pharmaceutical companies Pfizer and Moderna, the main producers of mRNA vaccines, are currently analyzing the clinical trials carried out by them to try to make a more thorough assessment of the possible effect that vaccination may have on pregnant women.

The United States (US) Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) are developing systems that offer the highest possible certainty to obtain information from the trials conducted so far on the effect of vaccination on pregnant women. In the meantime, while such reports are being obtained, the FDA states that pregnant women can be vaccinated against COVID-19 (2), a view also supported by the World Health Organization (WHO)(2,5), the American College of Obstetricians and Gynecologists (4), and the CDC (110). According to them, there is not enough medical evidence at this time to claim that there are specific risks that might outweigh the benefit of vaccination of pregnant women (2). In other words, in their opinion, the COVID-19 vaccine is not harmful to pregnant women (123 y 4), so vaccines should be available and administered to pregnant women who wish to be vaccinated.

However, the Royal College of Obstetricians and Gynaecologists and the Royal College of Midwives in the UK recommend that only two groups of pregnant women be vaccinated: a) those included in groups with high-risk medical conditions, since if they develop COVID-19, they may become severely ill; and b) those who belong to a group with high occupational risks, such as healthcare providers and carers in nursing homes. Therefore, both professional associations advise that if a woman is not included in either of the aforementioned two groups, she should not get vaccinated if she is pregnant. In the same vein, Public Health England’s Joint Committee on Vaccination and Immunisation recognizes the potential benefits of vaccination in women in high-risk groups and therefore recommends vaccination in these women only (2,5).

But what could be the reason for this difference of opinion between US and UK experts? Those in the UK argue that, since the action of the vaccines has not been sufficiently assessed in pregnant women, it is better to wait for more data to become available before recommending vaccination, except for pregnant women who are included in the aforementioned risk groups. In contrast, American experts think that pregnant women should be given the option to get vaccinated if they so wish (110).

In summary, in our view, it may be said that the medical evidence obtained from the clinical trials conducted so far is insufficient to ascertain the possible adverse effects of vaccination in pregnant women. Therefore, it seems sensible to postpone vaccination until the end of pregnancy, although it is advisable for pregnant women in the aforementioned risk groups to get vaccinated.

2. Could the embryo or fetus be affected if a pregnant woman is vaccinated?

So far, there is no medical evidence that mRNA vaccines against COVID-19 can affect the embryo or fetus of pregnant women  (1610), as the mRNA in the vaccine has a very short half-life and thus degrades easily after administration; this is why vaccines should be stored at very low temperatures and used promptly after preparation.

Once the vaccine has been injected, the small amounts of mRNA from the vaccine are destroyed by the body. Accordingly, it is virtually impossible for mRNA from the vaccine to cross the placenta to the fetus (1, 10).

3. Could the embryo or fetus be affected if a woman is vaccinated in circumstances where she can become pregnant and pregnancy occurs?

For women who may become pregnant immediately after receiving the vaccine, there is no medical evidence that the embryo or fetus may be adversely affected in these circumstances, because as we said, their cells (those of the woman) rapidly metabolize the mRNA of the vaccine, so it cannot affect the embryo or fetus. This supports the idea that it does not seem necessary to avoid pregnancy after vaccination. Nevertheless, for those women who still have doubts about what to do, the best solution might be to abstain from sexual intercourse for about 20 days after vaccination, since it is expected that the vaccine will no longer have any chance of affecting the embryo or fetus.

4. Can women be vaccinated while breastfeeding?

There appears to be no medical evidence of the likelihood that the vaccine might affect the nursing mother or her children. It can therefore be said that breastfeeding mothers can be vaccinated (1, 3, 10).

5. Could the vaccine affect a woman’s fertility?

There is no medical evidence of this. Thus, the Royal College of Midwives and the Royal College of Obstetricians and Gynaecologists say that there is no biologically plausible mechanism by which the COVID-19 vaccine would cause infertility in women (7911).

The British Fertility Society and the Association of Reproductive and Clinical Scientists have also published a document stating that there is “absolutely no evidence, and no theoretical reason, that any of the vaccines can affect the fertility of women or men” (7911).

6. Could pregnant women with COVID-19 develop a more serious disease than non-pregnant women?

Pregnant women with COVID-19 are at risk of developing a more severe illness than non-pregnant women of reproductive age (610). They may also be at increased risk for pregnancy and childbirth-related problems, especially premature delivery, hypertension, and postpartum hemorrhage (1210.).

Justo Aznar

Bioethics Observatory – Institute of Life Sciences

Catholic University of Valencia


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