Why does retrograde menstruation lead to endometriosis in some women and not in others?
A cada ciclo menstrual, fragmentos do endométrio podem percorrer um caminho inverso — pelas trompas, em direção à cavidade abdominal — num fenômeno chamado menstruação retrógrada. Esse processo é comum e, por si só, não representa doença; no entanto, em algumas mulheres, torna-se o ponto de partida para a endometriose, condição que afeta entre 5 e 15% das mulheres em idade reprodutiva. Desde a teoria de Sampson, em 1927, a ciência avança na compreensão de por que corpos semelhantes respondem de formas tão distintas — e a resposta parece residir na interseção entre genética, imunidade e ambiente hormonal. O que permanece urgente é que o diagnóstico tardio ainda rouba anos de qualidade de vida de inúmeras mulheres.
- A menstruação retrógrada ocorre na maioria das mulheres, mas apenas em algumas desencadeia endometriose — e a ciência ainda não sabe exatamente por quê.
- A doença avança em silêncio: muitas mulheres normalizam dores incapacitantes por anos antes de receber um diagnóstico correto.
- Mitos persistentes — como a crença de que gravidez cura a endometriose ou que exames normais descartam a doença — continuam afastando mulheres do cuidado que precisam.
- Pesquisadores investigam fatores genéticos, imunológicos e hormonais para entender o que diferencia quem desenvolve a condição de quem não desenvolve.
- A avaliação médica precoce diante de dor menstrual intensa ou sintomas pélvicos persistentes é o caminho mais eficaz para preservar fertilidade e qualidade de vida.
Todo mês, parte do tecido que reveste o útero não segue o caminho esperado. Em vez de sair pelo corpo, fragmentos do endométrio percorrem o trajeto inverso — pelas trompas de Falópio — e chegam à cavidade abdominal. Esse fenômeno, chamado menstruação retrógrada, é comum e não representa, por si só, nenhuma doença. É uma variação fisiológica, algo que o corpo simplesmente faz.
A confusão com a endometriose tem raízes históricas. Em 1927, o pesquisador Sampson propôs que essas células endometriais deslocadas poderiam se fixar em ovários, intestinos, bexiga ou no peritônio, sobreviver ali e continuar crescendo — causando dor, inflamação e infertilidade. A teoria explica muitos casos, mas não todos. A endometriose é multifatorial: envolve predisposição genética, alterações imunológicas, influências hormonais e processos inflamatórios. A pergunta central ainda sem resposta é por que a menstruação retrógrada leva à doença em algumas mulheres e em outras não.
O que torna essa questão urgente é o peso do diagnóstico tardio. Muitas mulheres vivem anos com dores severas antes de serem levadas a sério. Sintomas como dor que paralisa a rotina, dor durante relações sexuais, ao evacuar ou urinar, sangramento ligado ao ciclo menstrual e dificuldade para engravidar nunca deveriam ser normalizados. O mesmo vale para adolescentes, frequentemente orientadas a simplesmente esperar.
Mitos alimentam esse atraso: a ideia de que gravidez cura a endometriose, que exames de imagem normais descartam o diagnóstico, ou que toda mulher com a condição será infértil — todas falsas e prejudiciais. A mensagem dos especialistas é mais simples e mais esperançosa: quando a dor da mulher é levada a sério desde cedo, as chances de controlar os sintomas e preservar a qualidade de vida aumentam significativamente. Diagnosticar cedo não é apenas boa medicina — é reconhecer a experiência das mulheres como legítima.
Every month, most of what leaves a woman's body during menstruation flows out through the vagina, as expected. But not all of it. Some of the tissue lining the uterus—fragments of the endometrium—takes a different route. It travels backward, up through the fallopian tubes and into the abdominal cavity. This reversal is called retrograde menstruation, and it happens more often than many people realize.
The phenomenon itself is not a disease. It's a physiological event, something the body does, and it can occur in many women without causing any health problems at all. The backward flow happens because of the way the uterus contracts during menstruation, the shape and structure of the reproductive system, and the simple mechanics of how fluid moves through the body. Sérgio Podgaec, a gynecologist and president of the Brazilian Society of Endometriosis and Minimally Invasive Surgery, explains that this is simply how some bodies work—a normal variation in the process, not a pathology waiting to cause harm.
Yet retrograde menstruation has become inseparable in the public mind from endometriosis, a condition that affects between 5 and 15 percent of women of reproductive age. The connection traces back nearly a century, to 1927, when a researcher named Sampson proposed a theory that would shape how doctors understood the disease. His idea was straightforward: cells from the endometrium, traveling backward in the menstrual flow, could reach the pelvic cavity, attach themselves to the ovaries, intestines, bladder, or the tissue lining the abdomen, survive there, and continue to grow. Over time, this misplaced tissue could cause pain, inflammation, and infertility.
But Sampson's theory, while it explains many cases of pelvic endometriosis, does not explain all of it. The disease is multifactorial—it emerges from a combination of different factors working together in a woman's body. Researchers now know that risk increases with an early first menstruation, short menstrual cycles, or a family history of the condition, which may reflect a genetic predisposition that allows these cells to survive outside the uterus. Beyond that, scientists are investigating the role of immune system changes, hormonal environments, and inflammatory processes. The central puzzle remains: why does retrograde menstruation lead to endometriosis in some women and not in others? Researchers are still trying to understand whether there are differences in the amount, frequency, or characteristics of the menstrual material that flows backward in women who develop the disease compared to those who don't.
What makes this question urgent is that endometriosis, while common, is often diagnosed late. Many women live with severe pain for years before receiving a correct diagnosis, in part because the symptoms are normalized, treated as an inevitable part of having a period. But certain signs should never be accepted as normal: pain so intense it disrupts daily life, persistent pelvic pain, pain during sex, pain with bowel movements or urination, bleeding from the urinary tract or intestines tied to the menstrual cycle, significant fatigue, or difficulty becoming pregnant. These warrant medical evaluation. So do milder symptoms in adolescents, who are often told to wait, to see if things improve, to accept discomfort as part of growing up.
Podgaec emphasizes that several myths have delayed diagnosis and treatment for countless women. The belief that pregnancy cures endometriosis, that a normal imaging test rules out the disease, or that everyone with the condition will be infertile—these ideas are false and harmful. They keep women from seeking help. The reality is simpler and more hopeful: when suspicion is raised early, when a woman's pain is taken seriously, the chances of controlling symptoms, preserving quality of life, and planning appropriate treatment all increase. The longer diagnosis is delayed, the more the disease can progress, the more it can damage fertility and daily functioning. Early evaluation is not just a medical recommendation. It is an act of taking women's experience seriously.
Notable Quotes
In general, it is not considered an isolated disease, but a physiological phenomenon that can occur in many people.— Sérgio Podgaec, gynecologist and president of the Brazilian Society of Endometriosis and Minimally Invasive Surgery
The earlier a suspicion is raised, the greater the chances of controlling pain, preserving quality of life, and planning appropriate treatment.— Sérgio Podgaec
The Hearth Conversation Another angle on the story
So retrograde menstruation happens to a lot of women, but most of them never develop endometriosis. What's the difference?
That's the question researchers are still working to answer. It's not just about the backward flow itself. It seems to depend on whether the woman's body has the right conditions for those cells to survive and grow outside the uterus—genetics, immune function, hormonal environment, inflammation. It's a combination.
If it's so common, why is endometriosis still so often missed?
Because the pain gets normalized. Women are told cólicas are just part of having a period, that they should tough it out. By the time someone finally investigates, years have passed and the disease has had time to spread and cause real damage.
What would change if women got evaluated earlier?
Everything. Earlier diagnosis means better pain control, better chances of preserving fertility, and the ability to plan treatment before the disease progresses. It's not about curing something that can't be cured. It's about catching it before it takes over someone's life.
Are there warning signs that shouldn't be ignored?
Yes. Severe pain that interferes with work or school or sex. Persistent pelvic pain. Bleeding from the bladder or bowel. Fatigue that doesn't make sense. These aren't normal. They deserve investigation, even in teenagers.
And the myths—like pregnancy curing it—those are actually harmful?
Very much so. They give women false hope and keep them from seeking real treatment. They also suggest that if you can't get pregnant, the disease must be severe, which isn't necessarily true. The myths delay care.