Intrauterine synechiae are bands of scar tissue that form inside the uterus, sometimes extending into the cervix. When these adhesions cause symptoms like changes in menstrual bleeding, pelvic pain, or difficulty getting pregnant, the condition is called Asherman syndrome. About 19% of women develop some degree of intrauterine adhesions after a miscarriage treated with a surgical procedure, though many cases are mild and go undetected.
How Scar Tissue Forms in the Uterus
The inside of the uterus is lined with a layer of tissue called the endometrium, which thickens and sheds each month during a menstrual cycle. When the deeper layers of the endometrium are damaged, the body repairs the injury with fibrous scar tissue rather than normal lining. These scar bands can bridge across the uterine cavity, sticking the front and back walls together, or block off sections of the cavity entirely.
The adhesions range from thin, filmy strands that stretch easily to thick, dense bands of fibrous or even muscular tissue. Mild cases may involve less than 25% of the cavity. Severe cases can obliterate most or all of the uterine space, leaving little to no functional lining.
Common Causes
The vast majority of cases follow a surgical procedure inside the uterus, most often a dilation and curettage (D&C). This procedure uses instruments to remove tissue from the uterine lining and is commonly performed after a miscarriage, an elective termination, or to address a retained placenta after delivery. The risk increases with the timing and reason for the procedure:
- First-trimester pregnancy termination: up to 13% of women develop adhesions
- D&C after a late miscarriage: up to 30%
- Repeat procedures within two to four weeks of delivery or missed miscarriage: up to 23.4%
A meta-analysis in Human Reproduction Update found that among women treated surgically for miscarriage, roughly 1 in 5 developed adhesions. Notably, in one study within that review, women who were managed without surgery (either with medication or by waiting for the miscarriage to pass on its own) had zero cases of adhesions. This suggests the physical scraping of the uterine lining is the primary trigger, not the miscarriage itself.
Less commonly, infections can cause adhesions without any prior surgery. Genital tuberculosis is a well-known cause in parts of the world where TB is prevalent. Schistosomiasis, a parasitic infection, is another rare cause.
Symptoms to Recognize
The hallmark symptoms involve changes to your period. Periods may become noticeably lighter than before, or they may stop entirely. If scar tissue blocks the lower part of the uterus while the upper lining still functions, menstrual blood can become trapped, causing cyclical pelvic pain each month even though no bleeding is visible.
Many women first suspect a problem when they have difficulty becoming pregnant or experience recurrent miscarriages. Scar tissue can prevent an embryo from implanting properly or leave too little healthy lining to sustain a pregnancy. In milder cases, there may be no obvious symptoms at all, and the adhesions are discovered incidentally during a fertility evaluation or imaging study.
How Synechiae Are Diagnosed
Hysteroscopy is considered the gold standard. A thin camera is inserted through the cervix into the uterus, allowing a direct view of any scar bands, their thickness, and how much of the cavity they affect. This is the most reliable way to confirm the diagnosis and assess severity.
A hysterosalpingogram (HSG), an X-ray taken while dye is injected into the uterus, can also suggest adhesions. On HSG, synechiae appear as irregular filling defects that distort the normal outline of the uterine cavity. Unlike polyps or other growths, adhesions don’t get hidden when more dye is injected because no contrast can flow behind them. In severe cases, the entire cavity may appear shrunken or completely blocked, sometimes mimicking the appearance of a structural abnormality like a uterine septum. HSG gives useful information about the extent of scarring, but hysteroscopy is needed to confirm the diagnosis and plan treatment.
Severity is typically staged based on how much of the cavity is affected. Stage I means less than 25% involvement, while stage IV means more than 75% of the cavity is scarred over. A fully closed cervical opening automatically qualifies as at least stage II regardless of what the rest of the cavity looks like.
Surgical Treatment
The primary treatment is hysteroscopic adhesiolysis, a procedure where the scar tissue is cut and removed using a small camera and instruments passed through the cervix. No abdominal incisions are needed. The surgeon uses a thin electrosurgical loop or blade to carefully divide the adhesions while watching on a monitor. For extensive or dense scarring, ultrasound guidance through the abdomen is used simultaneously to help the surgeon avoid cutting through the uterine wall.
Newer bipolar instruments that work in a saline-filled environment have improved safety. If the instrument accidentally perforates the uterine wall, these systems are less likely to cause thermal injury to surrounding organs compared to older monopolar tools.
The goal is to restore a normal-shaped cavity with enough healthy lining to allow menstruation and, if desired, pregnancy. In a large cohort of 423 cases treated by a single experienced surgeon, 87.4% of women who attempted pregnancy afterward conceived. Women with moderate scarring (stage II) had the highest pregnancy rate at 94.5%. More severe cases had lower but still meaningful success rates.
Preventing Adhesions From Returning
Scar tissue has a tendency to reform after surgical removal, so several strategies are used in combination to keep the uterine walls separated during healing. Estrogen therapy is typically started immediately after surgery to stimulate regrowth of healthy endometrial lining. A common protocol involves taking estrogen daily for about 25 days, with progesterone added during the final days to trigger a withdrawal bleed, similar to a normal menstrual cycle.
A physical barrier is also placed inside the uterus to prevent the raw walls from sticking together while the lining regenerates. Options include a small balloon catheter inflated with saline, an intrauterine device (IUD), or a specially shaped silicone stent. Each has tradeoffs. Balloon catheters are inexpensive and simple but don’t conform well to the triangular shape of the uterine cavity, particularly near the upper corners. They also carry a small infection risk if left in place for an extended time. Silicone stents are designed to match the cavity’s shape more closely, keeping the walls separated while estrogen promotes healing.
A gel made from hyaluronic acid can be applied inside the uterus at the end of surgery as an anti-adhesion barrier. European guidelines give this approach a high recommendation, often in combination with a physical barrier. The stent or IUD is typically removed during a follow-up hysteroscopy two to three months later, which also allows the surgeon to check whether adhesions have reformed and address any new scarring early.