The effects of SARS-CoV-2 vaccination on pregnancy and birth

During pregnancy, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been associated with significant maternal morbidity and increased preterm birth rates. In accordance with the Centers for Disease Control and Prevention (CDC), the Mayo Clinic has reported that pregnant women who experience SARS-CoV-2 infection prior to delivery can have a higher likelihood of developing respiratory complications, which may even lead to necessary intensive care, compared to non-pregnant women.

The severe impact of this infection has given rise to a study by Theiler et al. (2021), which investigated the effects of SARS-CoV-2 vaccination in pregnancy in order to examine the protection it could provide to combat the infection.

Pregnant women were initially excluded from early clinical trials for SARS-CoV-2 vaccinations due to concerns over vaccine safety and efficacy, and so there is little data on outcomes after COVID-19 vaccinations for pregnant patients.

Study: Pregnancy and birth outcomes after SARS-CoV-2 vaccination in pregnancy. Image Credit: Natalia Deriabina / Shutterstock
Study: Pregnancy and birth outcomes after SARS-CoV-2 vaccination in pregnancy. Image Credit: Natalia Deriabina / Shutterstock

The Study

The new Mayo Clinic study utilized a comprehensive vaccine registry and a health system's delivery database to create a delivery cohort comprised of vaccinated patients. It looked at 2,002 patients in the delivery cohort, where 140 patients received the vaccination during pregnancy at a median gestational age of 32 weeks, and 212 patients developed the infection during their pregnancy. The vaccines given included three different vaccine manufacturers, Janssen, Moderna US, Inc., and Pfizer, Inc., and the number of doses given prior to delivery was noted.

In this study, maternal and neonatal complications were examined through a composite measure of pregnancy and delivery outcomes. A detailed summary of vaccination outcomes and pregnancy complications based on SARS-CoV-2 vaccination was recorded.

A pre-print version of the research paper is available on the medRxiv* server, while the article undergoes peer review.


The study found no maternal complications related to the SARS-CoV-2 infection occurred after vaccination during pregnancy and prior to delivery. In addition, there were no differences between vaccinated and unvaccinated pregnant patients when complications like thromboembolism and preterm birth were observed.

This indicated that although there was a decreased chance of vaccinated mothers contracting the SARS-CoV-2 infection compared to unvaccinated mothers, there was no evidence that infection itself increased the risk for complications during pregnancy or delivery. Unvaccinated pregnant patients did not appear to experience a greater level of SARS-CoV-2 infection than their vaccinated counterparts.

Sociodemographic Factors

The study found that associated factors affected the uptake of vaccination by patients when sociodemographic factors were taken into account. These associated factors included level of maternal education, pre-pregnancy BMI, use of infertility treatments for the pregnancy, as well as substance and tobacco use, ethnicity, as well as the number of pregnancies a patient has experienced.

The significance of this includes the study not being representative of pregnancies that are affected by these variables and, in turn, cannot comment on the effect of such pregnancies which have not taken the vaccination prior to delivery. Because these factors were not included, it is unlikely to be possible to observe their influence on pregnancy and birth outcomes, as well as any potential complications that may have occurred.

The Mayo Clinic has reported that pregnant patients who are Black or Hispanic can be more disproportionately impacted by the COVID-19 infection, and this effect may be even higher in individuals who have underlying health conditions, such as diabetes.

Substance Use

Approximately, 10.8% of adults in the US have a substance use disorder, including alcohol and tobacco use, which can have severe health effects. Chronic usage of these substances, including drugs, is associated with cardiovascular and metabolic diseases, consisting of arrhythmias, myocardial infarction, pulmonary hypertension as well as diabetes.

Despite the fact that substance use during pregnancy is discouraged, any current or historical use can have an impact on pregnancies, and ultimately the risk of COVID-19 infection during pregnancy.

The study investigated whether vaccinations during pregnancies would help with any pregnancy or delivery complications from COVID-19, and while the results may not be representative of all cases due to underlying medical issues, it concluded that those vaccinated have a decreased likelihood of experiencing the infection.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Marzia Khan

Written by

Marzia Khan

Marzia Khan is a lover of scientific research and innovation. She immerses herself in literature and novel therapeutics which she does through her position on the Royal Free Ethical Review Board. Marzia has a MSc in Nanotechnology and Regenerative Medicine as well as a BSc in Biomedical Sciences. She is currently working in the NHS and is engaging in a scientific innovation program.


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