Does the COVID-19 vaccine affect pregnancy and breastfeeding?

Since the first case was identified in the city of Wuhan (China, December 2019), the outbreak of SARS-COV-2 has changed our lives, and our conception of the world as we understood it before the pandemic. The irreparable loss of tens of thousands of human lives has been compounded by an economic, social and health crisis unprecedented in the last century.

The scale of the crisis is planetary. Having at least partially overcome the worst phase in terms of mortality (spring 2020), the advent of vaccination has opened the door to the hope of a medium-term resolution of the pandemic.

The first doses in our country were administered in December 2020. Currently, nearly 26 million people have already received the full vaccination schedule in our country, which represents more than 50% of the Spanish population.

In the field of reproductive medicine, and with the start of extensive vaccination of women of childbearing age, as well as the increase in cases in this population in recent months, concerns have arisen about the possible deleterious effects of the virus and its vaccine.

In the field of fertility, the first question is whether COVID infection or its vaccine can affect ovarian reserve. The hypothesis was raised by the discovery of virus receptors in the ovary, as well as menstrual cycle disturbances immediately after administration of the vaccine.

Early studies show no evidence that infection with the virus or its vaccine decreases fertility, as the sample sizes, follow-up time and internal validity of these studies are far from being statistically powerful enough to be categorical in this regard.

Although the guidelines of the Spanish Fertility Society are initially reassuring about the vaccine, arguing that the vaccines used in our population are not composed of live virus particles, it is true that not enough time has passed for a sufficiently extensive follow-up and documentation. Nothing is certain to date.

Vaccination and pregnancy

In the context of pregnancy, and considering that pregnancy is a risk factor for developing serious COVID infection, with obstetric complications derived from the same infection (miscarriage, prematurity), the recommendation is to be vaccinated. The vaccine also generates antibodies which, when transmitted to the foetus, create immunity.

Several questions arise in relation to vaccination. Taking the FACME and SEGO document as a reference, a series of recommendations are given in the light of current knowledge.

Which vaccines should be used in pregnant women? Based on the most experience with mRNA vaccines, these should be the vaccines of choice for vaccination of pregnant women (Pfizer and Moderna).

When to vaccinate pregnant women against Covid-19?

The risk of complications associated with COVID-19 infection, both for the pregnant woman and the foetus, is highest during the third trimester of pregnancy. Experience with vaccination in the first trimester of pregnancy is still very limited. In addition, the first trimester of pregnancy needs to be protected as much as possible. Therefore, it is reasonable to place vaccination from 20 weeks of gestation, after the period of highest theoretical risk to the foetus from the vaccine and before the highest risk of natural SARS-CoV-2 infection.

Some women ask us whether pregnancy should be avoided after vaccination. We reply that it is not necessary to wait a certain period of time between vaccination and pregnancy. According to the datasheet of the currently available vaccines, animal studies have shown no direct or indirect harmful effects with regard to reproductive toxicity.

Thus, it is also not justified to recommend termination of pregnancy after inadvertent vaccination of a pregnant woman, as the available data do not show direct or indirect harmful effects on the foetus. If a woman confirms that she is pregnant after having started vaccination, she should receive additional information on the new situation and, unless she decides against it, continue with vaccination.

Vaccination and breastfeeding

The COVID vaccine can be administered to breastfeeding mothers without any problems, so it is not recommended to stop breastfeeding after vaccination. If the patient develops COVID infection during breastfeeding, she can continue breastfeeding, if her clinical condition permits, while maintaining respiratory isolation measures as far as possible. In fact, the passage of antibodies has also been described through breast milk, which would represent a beneficial strategy for the newborn.

In conclusion, the evidence regarding COVID infection related to fertility and gestation is under continuous review, so nothing is to date definitive or categorical. It is the mission of institutions and individuals dedicated to health to keep abreast of new information that may emerge around the world, within the global nature of this pandemic.