It’s not true that nearly half of pregnant women in Pfizer’s COVID-19 vaccine trial miscarried

Since COVID-19 vaccines became widely available in the United States, PolitiFact has debunked several claims seemingly aimed at discouraging pregnant people from getting a shot. It’s not true, for example, that 920 women lost their babies after getting vaccinated. Nor that 80% of women who were vaccinated miscarried in the first trimester. 

But a recent Instagram post perhaps gave some expecting parents pause. 

"Massacre: Nearly half of pregnant women in Pfizer trial miscarried," the post said. "Forty-four percent of pregnant women who participated in the drug maker’s COVID-19 vaccine trial lost their babies." 

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The post cites "300,000 Pfizer documents" obtained through a Freedom of Information Act request. 

Pfizer declined to discuss the social media post, saying in an email that the company doesn’t "comment on social media claims." So we reached out to Jeffrey Morris, a director of the University of Pennsylvania’s biostatistics division. 

"It seems they misinterpreted the data," Morris said of the group behind the Instagram post.

He pointed us to a Aug. 12 story on the Daily Clout, a blog run by Naomi Wolf, who was banned from Twitter for spreading misinformation about vaccines. The story said a Pfizer document on "adverse events" from vaccines "reveals chilling data showing 44% of pregnant women participating in Pfizer’s mRNA COVID vaccine trial suffered miscarriages." 

It goes on to say that a section of the document "shows that 50 women became pregnant during the trial. However, one must dig through the rest of the large document to learn that 22 of the 50 women suffered ‘abortion spontaneous,’ ‘abortion spontaneous complete,’ ‘abortion spontenaous incomplete’ or ‘miscarriage.’"

That’s 44%. But by Aug. 19, the story, which has since been deleted, had a correction: "44% figure is incorrect. Two analysts have reviewed this Pfizer document and reached different totals and percentages than did the author of this report." 

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Morris did his own analysis of the data. The report contains a table showing 50 women reporting pregnancy after vaccination. There are also 22 reports of spontaneous abortion adverse events. But these 22 reports aren’t all unique — nine were mentioned twice. By Morris’ count, there were 13 miscarriages.

Among the group of 13, Morris said, three occurred among the 50 people who reported pregnancies after the first dose. 

As the 44% figure gained traction online, Victoria Male, an immunologist studying pregnancy at Imperial College in London, tweeted the actual miscarriage rates "among those who became pregnant during the trial." For the vaccine group, the rate was 7%. For the control group that didn’t take the vaccine, it was 15%. 

"These rates are not significantly different from each other, or from normal," Male said. 

The claim in the Instagram post is wrong on the math, and it is not proved that the smaller number of miscarriages happened because of a vaccine.

We rate this post False.