Related Experiment Video
Updated: Aug 3, 2025
Collection, Isolation, and Flow Cytometric Analysis of Human Endocervical Samples
Published on: July 6, 2014
Impact of coronavirus disease 2019 (COVID-19) vaccination on menstrual bleeding quantity: An observational cohort
Blair G Darney1,2, Emily R Boniface1, Agathe Van Lamsweerde3
1Department of Obstetrics & Gynecology, Oregon Heath & Science University, Portland, Oregon, USA.
Insights
COVID-19 vaccination did not significantly alter heavy menstrual bleeding days. A small, temporary increase in total bleeding quantity was observed after the first vaccine dose, resolving in the subsequent cycle.
Area of Science:
- Reproductive health
- Vaccinology
- Epidemiology
Background:
- Menstrual cycle changes are common and can be influenced by various factors.
- Understanding the impact of vaccination on menstrual health is crucial for public trust and informed decision-making.
Purpose of the Study:
- To investigate the association between COVID-19 vaccination and menstrual bleeding quantity.
- To determine if vaccination status affects the number of heavy bleeding days or overall bleeding volume.
Main Methods:
- A retrospective cohort study analyzed data from 9555 individuals using the Natural Cycles fertility app.
- Longitudinal Poisson generalized estimating equation and multinomial logistic regression models were employed.
- Data were adjusted for confounding factors to compare vaccinated and unvaccinated groups.
Main Results:
- No significant difference in the number of heavy bleeding days was found between vaccinated and unvaccinated individuals.
- A slightly higher proportion of vaccinated individuals reported increased total bleeding quantity after the first dose (4.0% adjusted difference).
- This increase in bleeding quantity was transient, resolving in the cycle following vaccination.
Conclusions:
- COVID-19 vaccination is associated with a small, temporary increase in total menstrual bleeding quantity.
- The number of heavy bleeding days remains unaffected by vaccination status.
- Findings suggest that any menstrual changes post-vaccination are minor and short-lived.
Objective:
To assess whether coronavirus disease 2019 (COVID-19) vaccination impacts menstrual bleeding quantity.
Design:
Retrospective cohort.
Setting:
Five global regions.
Population:
Vaccinated and unvaccinated individuals with regular menstrual cycles using the digital fertility-awareness application Natural Cycles°.
Methods:
We used prospectively collected menstrual cycle data, multivariable longitudinal Poisson generalised estimating equation (GEE) models and multivariable multinomial logistic regression models to calculate the adjusted difference between vaccination groups. All regression models were adjusted for confounding factors.
Main Outcome Measures:
The mean number of heavy bleeding days (fewer, no change or more) and changes in bleeding quantity (less, no change or more) at three time points (first dose, second dose and post-exposure menses).
Results:
We included 9555 individuals (7401 vaccinated and 2154 unvaccinated). About two-thirds of individuals reported no change in the number of heavy bleeding days, regardless of vaccination status. After adjusting for confounding factors, there were no significant differences in the number of heavy bleeding days by vaccination status. A larger proportion of vaccinated individuals experienced an increase in total bleeding quantity (34.5% unvaccinated, 38.4% vaccinated; adjusted difference 4.0%, 99.2% CI 0.7%-7.2%). This translates to an estimated 40 additional people per 1000 individuals with normal menstrual cycles who experience a greater total bleeding quantity following the first vaccine dose' suffice. Differences resolved in the cycle post-exposure.
Conclusions:
A small increase in the probability of greater total bleeding quantity occurred following the first COVID-19 vaccine dose, which resolved in the cycle after the post-vaccination cycle. The total number of heavy bleeding days did not differ by vaccination status. Our findings can reassure the public that any changes are small and transient.
More Related Videos
14:26A Method to Study the Impact of Chemically-induced Ovarian Failure on Exercise Capacity and Cardiac Adaptation in Mice
Published on: April 7, 2014
05:36Herbs-Partitioned Moxibustion on the Navel in a Rat Model of Primary Dysmenorrhea with Cold Coagulation and Blood Stasis
Published on: October 4, 2024
Related Concept Videos
01:22Hormonal Regulation of the Menstrual Cycle
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH...
01:29Bias in Epidemiological Studies
01:23Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast,...
01:27Confounding in Epidemiological Studies
01:19The Menstrual Cycle
The menstrual phase occurs from days 1 to 5 and involves the shedding of the stratum functionalis, as a...
01:24Disorders of the Female Reproductive System