An association between two factors is neutral when one does not influence the other. For example, we now know there is no significant relationship between COVID vaccines and early baby delivery. There have been concerns the vaccines affect menstrual cycle duration. However, new research found COVID vaccine neutral for menstrual length too.
What We Know About This New Research Project
U.S. National Institutes of Health noted reports of altered menstrual cycles during the early phases of the vaccination campaign. Accordingly, it invested more than $1.6 million in a research project. The results of this, the first study of the topic appeared in the journal Obstetrics and Gynecology on January 5, 2022.
The team consulted with over 3,900 U.S. female residents aged 18 to 45, and with a median cycle length of 28 days. Of these, approximately 2,400 (61%) were vaccinated. The researchers found:
1… The vaccinated group had their period less than one median day later, than before their vaccination.
2… However, those who had two mRNA vaccine doses in a single menstrual cycle had a median two-day delay.
3… The unvaccinated control group did not report any significant changes over the course of the study.
COVID Vaccination Was Neutral for the Menstrual Cycle Length But ….
There was no significant change to median menstrual length among the subject and control groups. Therefore we cannot explain away the slight delay in terms of general pandemic stress. However, the finding does appear to support a theory that triggering an immune response might affect the mechanism regulating menstrual timing.
Expert opinion on Washington Post’s Lily website describes the median timing difference as ‘really trivial’. That’s because ‘normal variations in the menstrual cycle can be up to eight days, and on average the median was less than one for the study.’ Therefore it seems the study makes a good case for COVID vaccine being neutral for menstrual length.
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Preview Image: The Normal Menstrual Cycle
Report in the Journal of Obstetrics and Gynecology
