The Science
Period Cramps 101: How & Why It Happens
If you’ve ever curled up in bed, clutching a hot water bottle, and cursing your uterus, you’re not alone! Menstrual cramps can be a downer during your monthly cycle, and almost everyone deals with a little bit of them.
The prevalence of dysmenorrhea can vary between 16% and 91% in individuals of reproductive age, with severe pain observed in 2% to 29% of individuals.1
So what causes these horribly painful cramps? And why do some people get them worse than others?
Whether your menstrual cramps are mild or debilitating, remember: your pain is valid, and there are options to help manage it. Your period shouldn’t control your life, and science is here to help us understand why it hurts – and what we can do about it.
The Science:
It turns out that there are a few different contributors to those dreadful monthly cramps:
PRIMARY DYSMENORRHEA
Prostaglandin
It is believed that prostaglandins (PGs) are the primary cause of dysmenorrhea. Women with dysmenorrhea have been found to have higher levels of PGs in their endometrial tissue and menstrual fluid. The menstrual cycle's declining hormone levels cause endometrial shedding to start.
The endometrial cells release progesterone throughout the period of endometrial shedding at the onset of menstruation. Uterine contractions are brought on by PGs, and the severity of the cramps is correlated with the amount of PGs released. Tissue hypoxia and ischemia brought on by uterine contractions result in pain, occasionally accompanied by nausea and diarrhea.2
Vasopressin has also been linked to primary dysmenorrhea. Vasopressin increases uterine contractility and can cause ischemic pain due to its vasoconstrictive effects.
Stress
During stress, our body releases adrenaline, estrogen, and prostaglandins continuously. Excessive production of estrogen and prostaglandins in the body during periods makes the uterus tighten up more, which results in more muscle tension and, thus, there is more pain. Increased adrenaline levels result in reduced blood flow to the body, resulting in cramps.3
Your Uterus!
Turns out, the position or shape of your uterus or cervix can make your cramps worse. Research has found a positive correlation between cervical length and the severity of period cramps.4 For instance, if your uterus tilts backward or your cervix is longer than average (average length of cervix 2.5cm), the contractions needed to shed the uterine lining may be more intense or painful.
SECONDARY DYSMENORRHEA
The common causes of secondary dysmenorrhea include endometriosis, fibroids, adenomyosis, endometrial polyps, interstitial cystitis, and pelvic inflammatory disease.
Endometriosis:
A condition in which tissues similar to the lining of the uterus grow outside the uterus, causing pain and inflammation.
Ovarian Cysts:
Ovarian cysts are fluid-filled sacs in the ovaries. Some have tissue inside them. The cysts are surrounded by a capsule and usually about the size of a cherry. Most ovarian cysts go away on their own.
These cysts often develop due to normal hormonal changes in puberty or during menopause. Sometimes ovarian cysts are already there at birth or are caused by something else, but that’s much less common.
Adenomyosis:
A condition in which the lining of the uterus grows into the muscle of the uterus, causing heavier bleeding and painful cramps.
Uterine Fibroids:
Uterine fibroids are benign (not cancerous) growths that develop from the muscle tissue of the uterus. They are the most common type of growth found in a woman's pelvis.
Pelvic Inflammatory Disease:
Pelvic inflammatory disease (PID) is defined as an inflammation of the upper genital tract due to an infection in women. The disease affects the uterus, fallopian tubes, and/or ovaries.
Mullerian Anomalies:
Müllerian duct anomalies (MDAs) are developmental disorders of the Müllerian duct, the embryonic anlage of most of the female reproductive tract. The prevalence of MDAs is 6.7% in the general female population and 16.7% in women who exhibit recurrent miscarriages.
Cervical Stenosis:
Cervical stenosis is the partial or complete narrowing or obliteration of the cervical canal, which may prevent access to the uterine cavity. It is commonly defined as the inability to pass a 2.5 mm cervical dilator through the cervical canal or when the external ostium measures less than 4.5 mm in diameter.
Pelvic Adhesions:
Adhesions are abnormal fibrous connections between tissues or organs in the abdomen, either between serosal surfaces or between a serosal and non-serosal surface.
They may appear as filmy/transparent or dense/opaque bands or as cohesive attachments without visible bands.
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