Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination: A U.S. Cohort

Alison Edelman; Emily R Boniface; Eleonora Benhar; Leo Han; Kristen A Matteson; Carlotta Favaro; Jack T Pearson; Blair G Darney

doi:10.1097/AOG.0000000000004695

Menstrual Cycle Cycle Physiology

Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination: A U.S. Cohort

Edelman A, Boniface ER, Benhar E, Han L, Matteson KA, Favaro C, Pearson JT, Darney BG

Published April 2022 Obstetrics and gynecology, 139(4), 481-489

DOI 10.1097/AOG.0000000000004695 PMID 34991109 PMC PMC8936155

RRM Academy Synopsis

COVID-19 vaccination is associated with under a one-day cycle change

A cohort study of 3,959 U.S. app users with regular cycles found that COVID-19 vaccination was associated with under a one-day change in cycle length. Vaccination was not associated with any change in menses length. Those who got both doses in one cycle had a larger lengthening that faded by cycle six.

Key Findings

Of 10,179 eligible individuals, 3,959 met inclusion criteria: 2,403 vaccinated and 1,556 unvaccinated, together contributing 23,754 cycles.
Unadjusted cycle length rose 0.71 days in the first dose cycle (98.75% CI 0.47–0.94) and 0.91 days in the second (98.75% CI 0.63–1.19). Unvaccinated cycles changed 0.07 and 0.12 days.
Adjusted differences between vaccinated and unvaccinated groups were 0.64 days for the first dose (98.75% CI 0.27–1.01) and 0.79 days for the second (98.75% CI 0.40–1.18).
Among 358 individuals who received both doses in one cycle, the adjusted difference was 2.32 days (98.75% CI 1.59–3.04). A rise of 8 days or more occurred in 10.6%, against 4.3% unvaccinated.
Adjusted menses length differed by 0.08 days for each dose (first dose 98.75% CI −0.04 to 0.19; second dose 98.75% CI −0.04 to 0.20).

Interpretation

The study is a retrospective cohort. Users of the Natural Cycles fertility-awareness app had logged their cycles ahead of time, and an unvaccinated group served as the comparison. Participants were U.S. residents aged 18 to 45 with regular cycles before vaccination. The results describe an association in the cycles when doses were given. By cycle six, the two-dose subgroup no longer differed significantly from the unvaccinated group. The authors point out that app users skew White, college educated and lower in body mass index than the national population.

RRM Context

Fertility awareness charting turns the cycle into measurable data. Here, each participant had her own three-cycle baseline, so a shift of a single day could be detected. Gynecology guidance treats a swing of up to a week as normal variation. The authors suggest that the immune stress of two doses early in the cycle could briefly affect the hormone signaling that governs follicle growth.

Our editorial summary of this paper, not the article's abstract.

Abstract

Objective

To assess whether coronavirus disease 2019 (COVID-19) vaccination is associated with changes in cycle or menses length in those receiving vaccination as compared with an unvaccinated cohort.

Methods

We analyzed prospectively tracked menstrual cycle data using the application "Natural Cycles." We included U.S. residents aged 18-45 years with normal cycle lengths (24-38 days) for three consecutive cycles before the first vaccine dose followed by vaccine-dose cycles (cycles 4-6) or, if unvaccinated, six cycles over a similar time period. We calculated the mean within-individual change in cycle and menses length (three prevaccine cycles vs first- and second-dose cycles in the vaccinated cohort, and the first three cycles vs cycles four and five in the unvaccinated cohort). We used mixed-effects models to estimate the adjusted difference in change in cycle and menses length between the vaccinated and unvaccinated cohorts.

Results

We included 3,959 individuals (vaccinated 2,403; unvaccinated 1,556). Most of the vaccinated cohort received the Pfizer-BioNTech vaccine (55%) (Moderna 35%, Johnson & Johnson/Janssen 7%). Overall, COVID-19 vaccine was associated with a less than 1-day change in cycle length for both vaccine-dose cycles compared with prevaccine cycles (first dose 0.71 day-increase, 98.75% CI 0.47-0.94; second dose 0.91, 98.75% CI 0.63-1.19); unvaccinated individuals saw no significant change compared with three baseline cycles (cycle four 0.07, 98.75% CI -0.22 to 0.35; cycle five 0.12, 98.75% CI -0.15 to 0.39). In adjusted models, the difference in change in cycle length between the vaccinated and unvaccinated cohorts was less than 1 day for both doses (difference in change: first dose 0.64 days, 98.75% CI 0.27-1.01; second dose 0.79 days, 98.75% CI 0.40-1.18). Change in menses length was not associated with vaccination.

Conclusion

Coronavirus disease 2019 (COVID-19) vaccination is associated with a small change in cycle length but not menses length.

Topics

Menstrual Cycle

Cycle Physiology Cycle Variability

Menstrual Cycle › Cycle Physiology › Cycle Variability

Alison Edelman, Emily R Boniface, Eleonora Benhar, Leo Han, Kristen A Matteson, Carlotta Favaro, Jack T Pearson, Blair G Darney

A Edelman, E Boniface, E Benhar, L Han, K Matteson, C Favaro, John Pearson, J Pearson, B Darney

PMID 34991109 34991109 DOI 10.1097/AOG.0000000000004695 10.1097/AOG.0000000000004695 Edelman et al. 2022, Edelman 2022

Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination: A U.S. Cohort

COVID-19 vaccination is associated with under a one-day cycle change

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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