MD REPORTS

MD REPORTS

Covid-19 vaccines and questions over miscarriage risk

Pregnant women were given sweeping assurances about Covid vaccine safety. But CDC data were flawed, animal studies raised questions, and officials privately discussed risks they could not rule out.

Maryanne Demasi, PhD's avatar
Maryanne Demasi, PhD
Aug 13, 2026
∙ Paid

Newly released text messages recovered from Anthony Fauci’s government phone expose a glaring contradiction at the heart of the Covid-19 vaccine rollout for pregnant women.

In January 2021—mere weeks after emergency authorisations began—Fauci privately raised a concern with then-CDC director Rochelle Walensky and incoming US Surgeon General Vivek Murthy:

“Since many people have significant cytokine storm and fever after the 2nd dose, this theoretically could be associated with miscarriage in the 1st trimester,” he wrote.

Walensky agreed, noting it was “definitely a good point, [especially] after dose two.”

That concern quickly escalated beyond just a theory.

Within weeks, mRNA pioneer Drew Weissman alerted Fauci to data showing that mRNA-LNPs administered to pregnant mice crossed the placenta, reached the foetus, and generated protein that triggered an immune response in the amniotic fluid.

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Weissman’s data established a plausible biological mechanism for miscarriage, showing that vaccine components could breach the placental barrier during a critical stage of foetal development.

Subsequent research reinforced those concerns. Studies have since shown that Moderna’s mRNA vaccine crossed the placenta of pregnant mice within an hour, entered the foetal circulation and accumulated in foetal tissue.

But none of this uncertainty ever made it into public messaging.

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