Stage 1 endometriosis is the mildest form of endometriosis, classified as “minimal” under the scoring system developed by the American Society for Reproductive Medicine (ASRM). It means small, shallow patches of endometrial-like tissue have been found growing outside the uterus, typically on the pelvic lining, with little or no scar tissue. Despite being labeled “minimal,” it can still cause significant pain and affect fertility.
How Stage 1 Is Defined
Endometriosis is classified into four stages using a point-based scoring system. A surgeon assigns points during a laparoscopy based on the size, depth, and location of tissue growths (called implants or lesions) and whether any scar tissue (adhesions) is present. A score of 1 to 5 points falls into Stage 1. Stages 2 through 4 represent progressively more widespread or deeper disease, with Stage 4 scoring 40 points or more.
In Stage 1, the implants are superficial, meaning they sit on the surface of pelvic tissues rather than burrowing deep into organs. There are few or no adhesions. The growths are typically scattered and small rather than clustered into large masses or cysts.
What the Lesions Look Like
During surgery, Stage 1 implants can look surprisingly different from one person to the next. Newer, more active lesions tend to appear as tiny red or clear vesicles, sometimes described as flame-like or polypoid. These are typically 1 to 3 millimeters across. Older lesions darken over time into the classic “gunshot” appearance: black, puckered spots surrounded by white scarring, and these can be 1 to 2 centimeters or larger. White lesions also occur and may represent earlier or less active disease. A person with Stage 1 may have just a handful of these small spots, most commonly on the peritoneum (the membrane lining the pelvis) or on the surface of the ovaries.
Pain Doesn’t Match the Stage
One of the most important things to understand about endometriosis staging is that the number on your surgical report does not predict how much pain you experience. A systematic review and meta-analysis found that pain intensity did not differ significantly between Stages 1/2 and Stages 3/4. Someone with a few tiny implants can have debilitating pain, while someone with extensive disease may have barely any symptoms at all.
The disconnect likely comes down to where the implants are located and how your nervous system responds to them, rather than how many implants there are. A single lesion on a nerve-rich area of the pelvic lining can generate more pain than a large cyst on the ovary. This is why a Stage 1 diagnosis should never be dismissed as “not that bad.” The staging system measures the physical extent of disease visible during surgery. It was not designed to measure suffering or predict quality of life.
Effects on Fertility
Even minimal endometriosis can interfere with getting pregnant, and it does so through several pathways at once. The pelvic environment changes: women with endometriosis have higher volumes of peritoneal fluid (the liquid inside the pelvis), and that fluid contains elevated levels of inflammatory molecules. These inflammatory signals can damage egg and sperm quality, interfere with fertilization, and make the uterine lining less receptive to an embryo trying to implant.
Ovulation itself can be disrupted. Endometriosis has been linked to problems with follicle development, a condition where the egg-containing follicle fails to release the egg properly, and hormonal imbalances during the second half of the menstrual cycle that make it harder to sustain an early pregnancy. The follicular phase (the first half of the cycle, when eggs mature) may also run longer than normal.
Transport of the egg through the fallopian tube can also go wrong. Research using specialized imaging found that 64% of women with endometriosis and open fallopian tubes still showed abnormal egg transport, meaning the egg traveled to the wrong tube or failed to move at all. That compares to 32% in a control group. Embryos from women with endometriosis also tend to develop more slowly in lab settings compared to embryos from women with other causes of infertility, suggesting the eggs themselves may be affected.
On the implantation side, the uterine lining may produce fewer of the adhesion molecules that a developing embryo needs to attach. Antibodies targeting the lining tissue have also been found at higher levels in some women with the condition. All of these factors can stack up, reducing the monthly chance of conception even when the disease looks minor on a surgical report.
Does Stage 1 Get Worse Over Time?
There is no reliable way to predict whether Stage 1 endometriosis will stay minimal, progress to a higher stage, or even regress on its own. Studies have not established clear progression rates, and many researchers emphasize that the natural course of the disease varies widely from person to person. Some women followed over time show no change at all, others show spontaneous improvement, and still others develop deeper or more widespread disease. Repeat surgery is the only way to re-stage the disease, so progression often goes untracked unless symptoms change significantly.
How Stage 1 Is Managed
Treatment depends on what’s bothering you most. For pain, hormonal therapies that suppress ovulation and reduce estrogen levels are a common first step. These include birth control pills, hormonal IUDs, and other medications that quiet the menstrual cycle and slow the growth of implants. Pain relief with anti-inflammatory medications is often used alongside hormonal treatment.
If pain is severe or does not respond to medication, surgical removal of the implants through laparoscopy is an option. During the same procedure used to diagnose and stage the disease, a surgeon can excise or ablate the visible lesions. For Stage 1, this is typically a short, outpatient procedure with a recovery period of a few days to two weeks. Some studies suggest surgical removal of even minimal implants can improve fertility rates, though the benefit is modest.
For women whose primary concern is getting pregnant, the approach shifts. Hormonal suppression isn’t useful for fertility because it prevents ovulation. Instead, options include surgical removal of implants followed by trying to conceive naturally, or moving directly to assisted reproduction such as intrauterine insemination or IVF. The right path depends on age, how long you’ve been trying, and whether other fertility factors are involved.
Because stage alone doesn’t capture the full picture of how endometriosis affects your body, treatment plans are typically built around your specific symptoms and goals rather than around the number on your surgical report.