(CNN) — It’s the claim that’s suddenly everywhere: The Covid-19 vaccine is going to make women infertile.

“No! You don’t know the science!” one woman posted on Twitter in response to naysayers. “The vaccine creates an immune response to the placenta and renders a woman sterile! They know this and this is the objective! It’s a shifty world sterilisation programme.”

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As it turns out, this unfounded fear isn’t new, said vaccine expert and pediatrician Dr. Yvonne Maldonado, the chief of Stanford University School of Medicine’s division of pediatric infectious diseases, who is currently leading vaccine trials in children younger than 12.

“Oh my goodness, people have been saying this about every vaccine since I can remember,” said Maldonado, who also chairs the American Academy of Pediatrics Committee on Infectious Diseases. “There is no evidence that this vaccine will affect development or fertility.”

Even those who do not consider themselves anti-vaxxers are expressing worry. As one woman shared on social media, “The protein that the covid vaccine codes for is similar to a protein on the placenta, so ppl worry it could cause infertility.”

Parents are expressing concern as well, as the US Centers for Disease Control and Prevention considers approving the Covid-19 vaccine for 12- to 15-year-olds this week.

To set the record straight, CNN reached out to Dr. Richard Beigi, who sits on the Immunization, Infectious Disease, and Public Health Preparedness Expert Work Group of the American College of Obstetricians and Gynecologists.

The conversation has been lightly edited for clarity.

CNN: Some people are worried that the Covid-19 vaccines could be associated with fertility issues for adult women and also for teenagers — when the vaccine for ages 12 to 15 becomes available.

Dr. Richard Beigi: There’s never been any vaccine that’s been linked with infertility.

There is no clear scientific reason to think the new vaccine would cause fertility problems in adults. Likewise, there’s no scientific reason to believe it would cause fertility problems in teenagers. Those are the facts, regardless of how old the person is.

It is a new mRNA vaccine technology being used in the Pfizer-BioNTech and Moderna vaccines, so I can understand theoretically how that would be unnerving to some people. But I think the more information we get, the more it shows that these new technologies are extremely effective. And in terms of vaccines, they’re quite safe.

Pregnancy is now clearly considered a high-risk category for the Covid-19 infection, as it is for other respiratory infections like influenza.

One has to weigh the risk of getting an infection versus the risk of taking the vaccine, and in in my estimation, these theoretical vaccine risks are getting weaker and weaker as we get more data.

CNN: Often people mention the Vaccine Adverse Event Reporting System, or VAERS, showing five examples of pregnancies connected to premature separation of the placenta that occurred in the same time frame as a Covid-19 vaccine.

Beigi: VAERS is basically a system where you report anything that happens to you after a vaccine. Just like getting the flu after a flu shot, these events were very likely to have already been under way when women received the vaccines, and then they became clinically recognized after the vaccine was given.

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There’s zero reason to believe any of these stories are related to the vaccine or caused by the vaccine.

If you read these reports in isolation, you would potentially be very scared. But these VAERS reports are not causal — they’re just coincidental. Here’s how we know.

Pregnant women weren’t part of the original clinical trials, but this year over 100,000 pregnant women have received one of the vaccines — mostly the mRNA vaccines of Moderna and Pfizer, but also some women have gotten the J&J vaccine.

We know this because 106,000 women who received the vaccine and signed up with government’s v-safe program said they were pregnant. Nearly 5,000 of those are being closely monitored via the CDC’s Vaccine Pregnancy Registry.

Sometimes pregnancies end in miscarriage or preeclampsia or abruption, and we know that. That’s why we’re looking at bigger groups of pregnant women who have taken the vaccine and comparing them to what we already know happens to pregnant women — and at what rates — before we had these vaccines.

As the data comes out, what we’re now seeing in these thousands of women who took the vaccine is that their pregnancy outcomes are no different than the population of pregnant women who did not get one of the vaccines.

This is very powerful because it doesn’t show any sign there’s a major issue and continues to validate what we thought — which was there’s no theoretical reason to believe these vaccines would be harmful.

CNN: Some people have posted concerns that the spike protein on the novel coronavirus will attach itself to similar receptors on the placenta and cause infertility.

Beigi: I fully understand that if people read a comment like that it could make them nervous. That’s fine, we respect that, and it’s why we talk to our patients about their concerns and counsel them.

The clinical data that continues to come out, doesn’t validate that issue as a concern. And that’s on top of the fact that, scientifically, it doesn’t make sense.

The placenta forms after conception — it actually comes from the baby’s tissue. So by definition, if you have formed a placenta, you are pregnant, you are not infertile.

It’s a new vaccine, it’s a scary disease, and people read these things online, which is all very understandable. I would think that hearing that thousands of pregnant women who have taken this vaccine and there are no signs of problems — I would hope for some people with concerns, that would be reassuring.

CNN: Many parents have said online that ‘It’s one thing for me as an adult to go out and get a shot in my arm but when I think about taking my child, that’s a whole other set of fears. I have to be super positive there’s nothing in any of these vaccines that’s going to harm my child’s future.” What’s your message to these parents?

Beigi: I fully understand being overly concerned about the future of your child. I have two teenage girls myself. And I am undoubtedly going to get my two teenage girls immunized when the vaccine is available in my area.

My message to parents is this: You have to weigh the risk of getting the Covid-19 infection versus the safety of the vaccines. The US Food and Drug Administration would not issue authorization for teens if there were major signs of problems. There was absolutely no reason to think there’s going to be new problems in this age group.

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