I finally caught COVID in January this year. I say “finally” because by then the Omicron variant was spreading like wildfire through the United States, and I was starting to feel like the last woman standing.
Fortunately, I didn’t get that sick, and it was over in less than a week—at least, my symptoms were. The impact on my cycle happened a little later, with delayed ovulation and, therefore, a later-than-expected-period. Fortunately, I chart my cycle using afertility awareness method(FAM), so I knew to expect a late period when I saw a late peak day (the term used for a charting woman’s best guess of the day of ovulation).
Being able to predict a late period is a great benefit of charting your cycle—but why does illness sometimes affect it in the first place? Cycle changes caused by sickness have to do both with how your body responds to the stress of being sick and where you’re at in your cycle when you get sick. COVID infection, like other types of illness, can also cause cycle changes.
How illness impacts hormones
Most of us have experienced firsthand the impact stress can have on our body, whether it’s insomnia, lack of an appetite, or just feeling run-down or tired. But stress can alsohave an impact on our hormones. For instance, stress occurring before ovulation can make the brain think that now is not a good time to get pregnant, which can then delay the release of the hormones that cause ovulation—and with late ovulation comes a late period. Ongoing stress can even keep ovulation from happening at all. If stress occurs after ovulation, it can cause a shorterluteal phaseand an early period. Again, the body’s response to the stressor isto try to prevent pregnancy, in this case by shortening the luteal phase to prevent successful implantation of a newly conceived zygote.
Illness can cause cycle changes because it’s a form of stress on the body. But that’s not all. The hormones that coordinate the menstrual cycle also directly interact with the immune system.As the authors of one study state, “The menstrual cycle is regulated by a complex interplay of hormones that interact with the immune, vascular and coagulation systems, and these interactions can influence menstrual bleeding and severity of (pre)menstrual symptoms” . For instance, they write, in the face of severe illness, your body can temporarily divert energy from the reproductive system to the immune system.
Notably,one recent studylooking at data from 43,999 recorded menstrual cycles from 1985 to 2016 suggests that minor illnesses such as a cold do not have an impact on a woman’s ability to get pregnant . In fact, they were associated with a statistically significant increase in conception rates, which the researchers speculated may be due to “a change in the immunological environment of the body and uterus.”This point seems to contradict the previous one?
It’s important to note that neither illness nor any other type of stressalwaysaffects your hormonal cycle—but they definitely can.
Your cycle phase can affect your illness, too
While being sick can affect your cycle, the reverse is also true: Your cycle can affect your illness. That’s because different hormones impact the immune system differently.For instance,whenestrogen is dominant(during the follicular phase),your body may react differently to illness than when progesteroneis dominant(during the luteal phase).One studyfound an increased risk for flu infection beginning at ovulation and continuing through the luteal phase . The researchers speculate that estrogen can boostimmunity while theprogesterone levels are low, as happens during the follicular phase.
According to a studyby researchers from Oxford University and the company that makes the cycle-tracking mobile appClue, “naturally cycling females exhibit menstrual variation in immune function and nonreproductive health” . As the co-author from Oxford, Dr. Alexandra Alvergne, toldRefinery29, “the whole function of the menstrual cycle is to produce cyclical patterns of immunity so actually we would be better to think of female health as cyclical” rather than as linear or constant.
In a2018 article, researchers looking at the impact of the hormonal cycle on anesthesia note that many studies have found that just before their menstrual period, women may experience “increased pain perception [and] exacerbation of systemic diseases” .
As early as 1998, researchers found that some diseases present different levels of symptom severity and clinical course based on the phase of the menstrual cycle . What’s more, hormonal fluctuations may exacerbate disease or impact the effectiveness of the drug or drugs used to treat the disease. The researchers called for better data on how drugs impact women at different phases of the cycle.
Unfortunately, the state of medical research has not improved much in that regard; the initial COVID-19 vaccine trials, for instance,required women to be on birth controlto participate—which meant that there was no data from those trials on how the vaccines might impact women experiencing real hormonal cycles (or pregnant women).According to aVerily MagazinearticlebyNatural Womanhood Editor Grace Emily Stark, this requirement is normal in pharmaceutical research.(clarify which requirement? To have non contraceptive women or to only have women on the pill?)
COVID-19 and cycle changes
Like me, many women have reported experiencing changes in their cycle after having COVID-19. Astudy published in December 2021reports several possible factors at play that may cause irregular or long cycles or heavy or prolonged menstruation . Notably, one of those factors is not a direct effect of COVID itself but, rather, the impact of stress resulting from living through a pandemic. The cycle phase during which a woman has COVID-19 may impact its severity, according to a study of patients with long COVID which found that over one-third experienced relapses during or before menstruation, “during the most inflammatory phases of the cycle.”
COVID treatments may also interact with hormones, the researchers note. One drug, dexamethasone, “may affect menstrual cycle patterns and blood loss,” and studies with non-human primates have found that anti-tumor necrosis factor monoclonal antibodies can impact the endometrium (they do not identify any research on the impact of the COVID monoclonal antibody treatment on the endometrium).
A reassuringstudy published in January 2022found that neither COVID-19 infection nor COVID-19 vaccination appear to impact women’s fertility, though the infection was associated with a short-term negative impact on men’s fertility .Another study, using a sample of women who use theNatural Cycles app, found that the vaccine was not associated with clinically significant changes in cycle length or menstruation length for women .We are not endorsing these vaccines, however, as too little research has been done to prove that they’re innocuous for women. We encourage everyone to make their own decision.
Use fertility charting to detect cycle changes with illness
If you’re charting your cycle, it’s a good idea to note in your chart any illness or symptoms you experience on the days you experience them. Then, at the end of a cycle, if you ovulate late, you can look back at your chart and see a possible explanation for why.
Additionally, if you track yourbasal body temperature (BBT), you should know that illness can throw off your temperature, even if you don’t have an actual fever. If you get sick, check with your instructor to see what your method recommends.
Imagine a world where women–and medical research–have this valuable information at their disposal, and can make health decisions that respect the uniqueness of their female bodies!
Minkowicz, C. “By What Mechanism Does Stress Affect Ovulation?”.The Science Journal of the Lander College of Arts and Sciences, vol. 11, no. 2, 2018.
 Sharp, Gemma C et al. “The COVID-19 pandemic and the menstrual cycle: research gaps and opportunities.”International journal of epidemiology, 2021. doi:10.1093/ije/dyab239
 Gnoth C, et al. “The impact of disturbances in natural conception cycles.”Arch Gynecol Obstet, vol. 301, no. 4, 2020, pp. 1069-1080. doi:10.1007/s00404-020-05464-y.
 Gulsah, Gabriel, Arck, Petra Clara. “Sex, Immunity, and Influenza.”The Journal of Infectious Diseases, vol. 209, issue _suppl3, 2014, pp. S93-S99.https://doi.org/10.1093/infdis/jiu020
 Alvergne, A, Hogqvist Tabor, V. “Is Female Health Cyclical? Evolutionary Perspectives on Menstruation.”Trends in Ecology & Evolution, vol. 33, no.6, 2018, pp. 399-414. DOI:https://doi.org/10.1016/j.tree.2018.03.006
 Kurdi, Madhuri S, and Ashwini H Ramaswamy. “Does the phase of the menstrual cycle really matter to anaesthesia?.”Indian journal of anaesthesia,vol. 62, no. 5, 2018, pp. 330-336. doi:10.4103/ija.IJA_139_18
Kashuba, A.D.M., Nafziger, A.N. “Physiological Changes During the Menstrual Cycle and Their Effects on the Pharmacokinetics and Pharmacodynamics of Drugs.”Clin Pharmacokinetvol. 34, 1998, pp. 203–218.https://doi.org/10.2165/00003088-199834030-00003
Sharp, Gemma C et al. “The COVID-19 pandemic and the menstrual cycle: research gaps and opportunities.”International journal of epidemiology, 2021. doi:10.1093/ije/dyab239
 Wesselink, Amelia K, et al. “A Prospective Cohort Study of COVID-19 Vaccination, SARS-CoV-2 Infection, and Fertility.”American Journal of Epidemiology, 2022. https://doi.org/10.1093/aje/kwac011
 Edelman, Alison, et al. “Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination.”Obstetrics & Gynecology. 2022. doi: 10.1097/AOG.0000000000004695
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