Steve Kirsch claims in Should you get vaccinated?:
82% miscarriage rate in first 20 weeks (10% is the normal rate).
Is this claim that the miscarriage rate is significantly increased through COVID-19 vaccinations backed up by data or bogus?
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The referenced claim misuses statistics from a study of the vaccines effects based on V-Safe data. The study finds that of 824 completed pregnancies of vaccinated women, 104 of the pregnancies were completed due to miscarriage. The letter to the editor claims that in 700 of the pregnancies, the vaccine was administered after 20 weeks when women are at much lower risk of miscarriage; if you exclude those from the results, you get the supposed 82.5% rate of miscarriage.
What this analysis ignores is that the vast majority of women who received the vaccine before 20 weeks and did not miscarry had not yet carried their pregnancies to term at the time the data were collected and thus were not included in the statistics of completed pregnancies. In fact, if we assume that vaccinations were distributed evenly across the term of pregnancy, you would expect that about 700 women would be vaccinated before 20 weeks if 700 were vaccinated after. Since only 126 of the pregnancies were completed, that would mean there were 574 non-miscarried pregnancies not accounted in the statistics. This indicates that the methodology used by the original researchers, counting miscarriages against total completed pregnancies, was the sound one.