COVID-19 vaccines don’t increase the incidence of poor outcomes during pregnancy, according to current safety data on COVID-19 vaccines

COVID-19 vaccines caused miscarriages
Inadequate support: Simply because a miscarriage occurred after vaccination doesn’t mean that the vaccine caused the miscarriage. While temporality, or the occurrence of one event after another, is essential for drawing a causal association between two events, it is insufficient on its own to demonstrate causality. Scientific evidence so far doesn’t show an increased incidence of miscarriages in pregnant women who received the COVID-19 vaccine.
COVID-19 vaccines authorized for emergency use by the U.S. Food and Drug Administration showed a high level of safety and efficacy in clinical trials. However, these trials excluded pregnant women. For this reason, data from clinical trials regarding the vaccines’ safety and efficacy in pregnant women is limited. However, current safety monitoring of pregnant women who received the vaccine hasn’t shown an increased incidence of pregnancy-related adverse events compared to unvaccinated pregnant women. The U.S. Centers for Disease Control and Prevention stated that “People who are pregnant and part of a group recommended to receive COVID-19 vaccine, such as healthcare personnel, may choose to be vaccinated”.

FULL CLAIM: COVID-19 vaccines caused miscarriages


Facebook posts claiming that the COVID-19 vaccine caused a healthcare worker to have a miscarriage went viral in early February 2021. These posts (see example) show a photo of a healthcare worker receiving a COVID-19 vaccine and tweets by physician Sara Beltrán Ponce about her vaccination and later miscarriage. The juxtaposition of the photo and the tweets leave readers with the impression that the woman in the photo is Sara Beltrán Ponce.

The content of many of these Facebook posts can be traced to a tweet published on 6 February 2021 by a user named Steve, which itself received a high level of interactions on Twitter, with more than 14,000 likes and more than 5,900 retweets. The tweet was picked up by others, including Paul Joseph Watson, a conspiracy theorist and editor for InfoWars.

As the fact-checking organizations Observador and Maldita pointed out in their debunks, the woman in the photo of these posts is not Sara Beltrán Ponce, but a nurse named Amy Guy-Ulrich. Guy-Ulrich posted a photo of herself receiving the COVID-19 vaccine in the Facebook group Hearts for Healthcare Workers on 6 January 2021. Other members of the group later alerted her to the inaccurate posts that claimed she had had a miscarriage; Guy-Ulrich refuted the claim on 6 February, stating in a Facebook comment that she was “happy, healthy, and pregnant! 32 weeks with a perfectly healthy big baby boy!”

Apart from the misidentification of the woman in the photo, the tweets on their own don’t prove that the COVID-19 vaccines cause miscarriage. This is an example of the logical fallacy known as post hoc ergo propter hoc, as the claim is based solely on the fact that the miscarriage happened after the vaccination, without any other evidence for support.

While temporality, or the occurrence of one event after another, is essential for drawing a causal association between two events, it is insufficient on its own to demonstrate causality (necessity vs. sufficiency).

Therefore, in order to claim that the COVID-19 vaccines cause miscarriages in pregnant women, one important step is to compare the rates of miscarriage in vaccinated and unvaccinated women and show that the rate is significantly higher in vaccinated women, rather than simply point to the occurrence of miscarriages in vaccinated women.

Some social media users also pointed to VAERS reports of spontaneous abortions in women who received COVID-19 vaccines as evidence (see example). VAERS, or the Vaccine Adverse Events Reporting System, serves as “a national early warning system to detect possible safety problems in U.S.-licensed vaccines”, which “can provide CDC and FDA with valuable information that additional work and evaluation is necessary to further assess a possible safety concern”. But as in the case of the tweets, VAERS collects information about adverse events occurring following vaccination. These reports alone aren’t evidence that the vaccine caused the adverse events, and VAERS clearly states that its data is not meant to demonstrate a causal relationship between an adverse event and a vaccine.

So far, two COVID-19 vaccines are authorized for emergency use by the U.S. Food and Drug Administration, one by Pfizer and BioNTech and the other by Moderna. There is limited data on the vaccines’ safety and efficacy in pregnant women, as the clinical trials for the vaccines excluded pregnant women. Beate Kampmann, a professor of pediatric infection and immunity at the London School of Hygiene and Tropical Medicine, explained the reason for this in a Nature article:

This has little to do with any vaccine issues but everything to do with pregnancy itself. Miscarriages, premature births and stillbirths are unfortunate but not infrequent outcomes of pregnancies. It is important to emphasize that so far, no vaccines routinely recommended in pregnancy (vaccines against tetanus, influenza and whooping cough) have shown an increase in rates of poor pregnancy outcomes in vaccinated pregnant women versus those who are not vaccinated. However, for the inclusion of pregnant women in trials of novel vaccines, including those directed against SARS-CoV-2, tighter observations during pregnancy and after delivery are needed in order to confirm that any adverse outcomes of pregnancy are not related to vaccination. Follow-up of the newborns is also required, given that theoretically, a vaccine given in pregnancy could also affect the offspring.

Due to these added complexities, manufacturers shy away from including pregnant people in vaccine studies, and therefore, no safety data currently exist for pregnant women or infants.

However, some participants in the clinical trials for COVID-19 vaccines became pregnant over the course of the trial. The Vaccines and Related Biological Products Advisory Committee that reviews the safety, effectiveness, and appropriate use of vaccines published briefing documents that detailed the outcomes in pregnant trial participants.

For the Pfizer-BioNTech vaccine, the briefing document stated:

Twenty-three pregnancies were reported through the data cut-off date of November 14, 2020 (12 vaccine, 11 placebo). […] Unsolicited [adverse events] related to pregnancy include spontaneous abortion and retained products of conception, both in the placebo group.

For the Moderna vaccine, the briefing document stated:

Thirteen pregnancies were reported through December 2, 2020 (6 vaccine, 7 placebo). […] Unsolicited [adverse events] related to pregnancy include a case of spontaneous abortion and a case of elective abortion, both in the placebo group.

That said, these numbers are too small to provide any meaningful information about the safety of the COVID-19 vaccines in pregnant women. As such, researchers planned clinical trials that include pregnant women specifically to address the question of the vaccines’ safety and efficacy in pregnant women. A trial for the Pfizer-BioNTech COVID-19 vaccine in pregnant women was announced on 18 February 2021.

Given the uncertainty and the observation that pregnant women are more likely to develop severe COVID-19, the U.S. Centers for Disease Control and Prevention (CDC) released guidance to help pregnant women decide whether they should get the COVID-19 vaccine. The CDC stated:

Until findings are available from clinical trials and additional studies, only limited data are available on the safety of COVID-19 vaccines, including mRNA vaccines, administered during pregnancy:

  • Limited data are currently available from animal developmental and reproductive toxicity studies. No safety concerns were demonstrated in rats that received Moderna COVID-19 vaccine before or during pregnancy; studies of the Pfizer-BioNTech vaccine are ongoing.
  • Researchers have studies planned in people who are pregnant.
  • Both vaccine manufacturers are monitoring people in the clinical trials who became pregnant.

CDC and the Food and Drug Administration (FDA) have safety monitoring systems in place to capture information about vaccination during pregnancy and will closely monitor reports.

mRNA vaccines do not contain the live virus that causes COVID-19 and, therefore, cannot give someone COVID-19. Additionally, mRNA vaccines do not interact with a person’s DNA because the mRNA does not enter the nucleus of the cell. Cells break down the mRNA quickly. Based on how mRNA vaccines work, experts believe they are unlikely to pose a specific risk for people who are pregnant. However, the actual risks of mRNA vaccines to the pregnant person and her fetus are unknown because these vaccines have not been studied in pregnant women.

The American College of Obstetricians and Gynecologists (ACOG) stated:

While safety data on the use of COVID-19 vaccines in pregnancy are not currently available, there are also no data to indicate that the vaccines should be contraindicated, and no safety signals generated from Developmental and Reproductive Toxicity (DART) studies for the Pfizer-BioNtech and Moderna COVID-19 vaccines.

In addition, “ACOG recommends that COVID-19 vaccines should not be withheld from pregnant individuals who meet criteria for vaccination based on [Advisory Committee on Immunization Practices]-recommended priority groups”.

More than 20,000 pregnant women received the COVID-19 vaccine in the U.S., and there have been “no red flags”, said Anthony Fauci, the director of the U.S. National Institute of Allergy and Infectious Diseases.


Published on: 19 Feb 2021 | Editor:

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