Fact check: Pfizer, Moderna vaccines don't pose 'any obvious safety signals' in pregnancy, study found

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The claim: CDC manipulated data about miscarriage rate in pregnant, vaccinated women

The different coronavirus vaccines have one thing in common: They've been met with skepticism by some Americans, who have often shared misinformation about their potential side effects.

Many of these false claims center around pregnant women.

"The CDC have been caught manipulating data to justify giving pregnant women the COVID jab," an image posted July 10 on Instagram says. "Their study stated just 12% of women suffered a miscarriage after having the jab, the actual figure was 82%."

The image is a screenshot of a July 6 tweet by the Daily Expose, a London-based alternative news site that has previously shared misinformation regarding vaccine safety. The tweet was retweeted nearly 2,000 times in the first week, and the Instagram post has received over 1,200 likes since it was posted on July 10.

The post refers to an April 21 study from researchers at the U.S. Centers for Disease Control and Prevention and published by the New England Journal of Medicine.

A similar Instagram post claimed women who got vaccinated within 30 days to 20 weeks of becoming pregnant had an 82% miscarriage rate. The image received more than 6,400 likes before it was deleted.

The study researched the safety of COVID-19 vaccines based on messenger RNA, or mRNA, in pregnant women between Dec. 14, 2020, and Feb. 28.

The Instagram user told USA TODAY he shared the image because several women had messaged him "expressing concerns over changes in their menstrual cycle."

False claims about the vaccine harming pregnant women aren't new.

USA TODAY has previously debunked other false claims about the vaccine causing infertility in women, miscarriages increasing since the vaccine rollout, and vaccines causing menstrual cycle changes.

This claim is also wrong.

The study data released so far actually showed only 12.6 % of pregnant women in the study had a miscarriage – not 82%. The study concluded that vaccinations weren't a safety risk for pregnant women.

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The Daily Expose, along with social media users who've shared the claim, reached the errant conclusion by altering the data that scientists used, experts say.

Study found no safety concerns in pregnancy caused by vaccines

The study used data from three main data-collecting programs within the CDC: the V-safe Pregnancy Registry, the V-safe smartphone tool and the Vaccine Adverse Event Reporting System, or VAERS.

A total of almost 4,000 women from the pregnancy registry participated in the study. Of that group, 827 participants completed their pregnancy by the end of the study, a category that included healthy births, miscarriages and any other complications that ended the pregnancy.

Among those 827 completed pregnancies, 712 gave birth and 104 had a miscarriage. One case resulted in a stillbirth, and 10 resulted in either induced abortion or extrauterine pregnancy.

Those completed pregnancies consisted primarily of women at the very beginning or very end of their terms. The live birth group was, of course, at the end, and the miscarraiges generally occurred among those early on.

Out of the 104 miscarriages, 94 occurred within the first 13 weeks of the pregnancy – the first trimester, which is when most miscarriages happen according to the Mayo Clinic.

That works out to a miscarriage rate of 12.6%. According to Mayo Clinic, that percentage is within the average miscarriage rate for the population at large, which is between 10% and 20%.

The researchers made it clear that the data is preliminary, and that "continued monitoring is needed to further assess" possible effects in pregnancies associated with the vaccines.

"The findings may change as additional pregnancy outcomes are reported and the sample size increases, which may facilitate detection of rare outcomes," the study said.

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Martha Sharan, a spokesperson for the CDC Vaccine Task Force, said experts are currently analyzing the most recent data from over 1,000 other participants who were vaccinated in their first trimester. A report is forthcoming.

Daily Expose article skewed data

The Daily Expose article linked on the image shared on Instagram claims women who were vaccinated within the first 20 weeks of their pregnancy had an 82% rate of miscarriage.

The publication altered the data used to calculate the miscarriage rate in order to get that percentage. Researchers divided 104 – the number of miscarriages recorded – by 827 – the total number of completed pregnancies at the time of analysis.

But the article argued because the 700 women who had live births were vaccinated in their third trimester, when miscarriages are less common, they shouldn't be used as part of the sample to analyze the miscarriage rate.

So, the Daily Expose changed the denominator and divided 104 by 127, which it claims is the number of women who were pregnant and were vaccinated in their first or second trimester. That results in the claimed 82% miscarriage rate.

But that change doesn't portray the data accurately, according to Sharan.

"This is not an appropriate calculation based on the data available because more than 1,000 pregnancies (from those vaccinated in the first and second trimester) were ongoing, and their outcome data wasn't available at the time of the report," she said.

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Other experts agree.

Victoria Male, a reproductive immunology lecturer at Imperial College, called the new percentage "a meaningless statistic" in a Twitter thread.

Male explained why the reasoning is flawed: Using that new denominator only takes into consideration completed pregnancies in the first and second trimester, in which a miscarriage is the only result possible.

"Presumably the only reason that rate isn't 100% is because some people vaccinated at the end of the 2nd trimester completed their pregnancies within three months by giving birth," she tweeted.

Our rating: False

We rate the claim that a study found vaccinated, pregnant women had an 82% rate of miscarriage FALSE, based on our research. The claim is based on a mischaracterization of the data available, experts say. The process used to come up with the 82% figure ignores any women who were vaccinated in the first and second trimester and didn't miscarry, data thathas not yet been released.

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This article originally appeared on USA TODAY: Fact check: Covid-19 vaccines not risky for pregnant women, study says

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