Women have been reporting menstrual irregularities post COVID-19 vaccine. I’ve written about that phenomenon here. At this point it is unknown if this is a true side effect (like fever, or swollen lymph nodes), or if this represents sampling bias, meaning the menstrual irregularities are due to something else or are simply the normal background rate and being misattributed to the vaccine.
Since first writing about this, more than 50 women have reached out to report their own menstrual irregularities. Three of them were post menopausal (meaning more than one year after their last menstrual period). This deserves a discussion, as bleeding after menopause should never be brushed off as one last trip across the crimson bridge.
When you are in postmenopause (one year or more from your last period) nothing—not even a vaccine—knocks a rogue egg back into action. Any bleeding here is not menstruation, it is called postmenopausal bleeding, and is abnormal and needs to be investigated, whether it’s a pinkish tinge or a heavy flow.
Up to 11 percent of women have bleeding after menopause and it happens most often in the first three years, so it’s easy to see how people might think this was one last menstrual hurrah. While it can happen for benign reasons (see the list below), it can also be a sign of endometrial cancer or cancer of the lining of the uterus. Overall, the risk of this cancer with post menopausal bleeding is approximately 6-10%, but for some women that risk may be higher and for others it may be lower (the range of cancer risk is from as low as 1% to as high as 28%). Bleeding after menopause is so sensitive a sign of cancer that 90% of women who have endometrial cancer report they had some bleeding before they were diagnosed.
Factors that increase the risk that bleeding after menopause could be cancer include the longer the time from the last menstrual period, family history of endometrial cancer, type 2 diabetes, taking estrogen without a progestogen (progesterone or a progestin, which is a progesterone-like hormone), taking the medication tamoxifen, and obesity (fatty tissue produces estrogen, and estrogen is a trigger for this cancer). Factors that lower the risk of endometrial cancer are a history of taking birth control pills or having the levonorgestrel IUD.
There are also benign (non cancerous) causes of bleeding after menopause, including the following:
A thin uterine lining (endometrium): Without estrogen the lining can get very thin and the tissue can break down spontaneously causing bleeding. Think of this like a skinned knee, although it’s not painful. This can also happen for women in postmenopause who are not taking hormones and for those taking menopausal hormone therapy (MHT) if the amount of estrogen is too low relative to the progestogen (progesterone or progesterone-like hormone)
A thick uterine lining: This is due to too much estrogen relative to progestogen. The source of this estrogen could be menopausal hormone therapy (MHT), supplements that have been adulterated with hormones, or from fatty tissue. Women who take estrogen in their MHT and rely on topical progesterone are at risk here as progesterone cannot be absorbed through the skin. (Run away from any doctor recommended topical progesterone cream!)
A polyp: An overgrowth of tissue in the lining of the uterus.
Blood thinners: Even when a woman is taking these, precancer and cancer must be considered.
Medications: Steroid injections, for example, in an epidural for back pain, can lead to bleeding.
Genitourinary syndrome: The blood on a pad may not be from the uterus and instead may be from the vaginal tissues, which can get fragile from lack of estrogen and bleed easily. This is called genitourinary syndrome of menopause or GUSM.
We have no idea if the vaccine can trigger benign post menopausal bleeding, but biologically it seems that a vaccine is far less likely to be a potential trigger for bleeding after menopause. The endometrium is less active immune-system wise. In addition, post menopausal bleeding is a something that almost certainly would have been reported as an adverse event in vaccine studies, either during the study or afterwards in post marketing surveillance. Meaning if it were a vaccine-related side effect we’d likely know by now. As more data emerges we will hopefully know more.
It isn't possible to know the cause of bleeding after menopause by the bleeding pattern (meaning how much, or when it happens), so all bleeding after menopause should be reported to your medical provider. Please don’t think of this as a period. The next steps will involve assessing your cancer risk and either an ultrasound of the lining of the uterus or a sampling of cells from the lining of the uterus (a test called an endometrial biopsy).
And for those who want to know much more about irregular bleeding during the menopause transition (premenopause) and beyond, or about menopause in general, I’ve got you covered with The Menopause Manifesto, which is out May 25.