The presence of scar tissue on the uterus, medically known as intrauterine adhesions or synechiae, can complicate conception and pregnancy. While it does not automatically prevent pregnancy, the severity and location of this fibrotic tissue determine the potential challenges a person may face. These adhesions can range from thin bands of scar tissue to thick formations that cause the walls of the uterus to stick together, partially or completely distorting the normal shape of the cavity. Understanding how this scarring develops and interferes with the reproductive process is the first step toward seeking appropriate medical help.
Primary Causes of Uterine Scarring
Uterine scarring almost always occurs as a response to trauma to the endometrial lining. The most common cause is a procedure called Dilation and Curettage (D&C), particularly when performed after a miscarriage, retained placenta, or abortion. If the scraping during a D&C is too deep or aggressive, it can damage the basal layer of the endometrium, which regenerates the healthy uterine lining.
Other uterine surgeries also carry a risk, including a myomectomy (surgical removal of uterine fibroids). Cesarean sections (C-sections) can lead to scar tissue formation at the incision site on the lower uterine segment. Extensive intrauterine adhesions can lead to a condition known as Asherman’s Syndrome, where the uterine walls become partially or completely fused.
How Scar Tissue Affects Conception
The primary function of the uterine lining is to provide a receptive environment for a fertilized embryo to implant, which relies on a thick, healthy endometrium. Scar tissue physically reduces the functional surface area of the endometrium, making successful implantation difficult or impossible. This fibrotic tissue often lacks the robust blood supply necessary to nourish a developing embryo.
Scar tissue can replace healthy endometrial tissue, resulting in a thinner uterine lining that cannot support the early stages of pregnancy. In severe cases, dense adhesions can physically block the passage of sperm from the cervix into the fallopian tubes, preventing fertilization. The physical distortion of the uterine cavity further compromises the architecture necessary for the embryo to securely attach and grow.
Pregnancy Complications Linked to Uterine Scars
Once a pregnancy is established in a scarred uterus, risks emerge centered around placental development and uterine structural integrity. Scarring increases the chance of the placenta implanting in an abnormal location, such as Placenta Previa, where the placenta covers the opening of the cervix. More concerning is the risk of the placenta implanting directly into the scar tissue, resulting in a condition called Placenta Accreta, Increta, or Percreta.
Placenta Accreta occurs when the placenta grows too deeply into the uterine wall, sometimes invading the muscle (Increta) or penetrating through the wall (Percreta). This condition is highly associated with prior C-sections, with the risk rising significantly with each subsequent C-section. Scar tissue can also increase the likelihood of second-trimester miscarriage and preterm labor.
A serious risk for those with prior C-sections or extensive myomectomies is uterine rupture. This complication, while rare, involves the scar tearing open, most commonly during labor in the third trimester. The risk of rupture is four times higher when the interval between a C-section and the next pregnancy is less than six months. Close monitoring is necessary throughout the pregnancy, especially for those with multiple prior uterine surgeries.
Diagnosis and Fertility-Preserving Treatments
A physician typically uses specialized imaging techniques to diagnose and assess the extent of intrauterine adhesions. A Hysterosalpingogram (HSG) uses X-ray dye to visualize the uterine cavity and fallopian tubes, identifying blockages or irregularities in shape. Saline Infusion Sonohysterography (SIS) involves infusing sterile saline into the uterus during an ultrasound, which distends the cavity to provide a clearer view of the lining and any adhesions.
The gold standard for both diagnosis and treatment is operative hysteroscopy. This minimally invasive surgical procedure involves inserting a thin, lighted telescope into the uterus through the cervix to directly visualize the scar tissue. The surgeon then uses fine instruments to carefully cut and remove the adhesions, restoring the normal size and shape of the uterine cavity.
Following surgery, several measures are taken to prevent the reformation of scar tissue. This often includes the temporary placement of a balloon or a special gel barrier inside the uterus to keep the walls separated during healing. Patients are also commonly prescribed high-dose estrogen therapy to stimulate the regrowth of a healthy, thick endometrial lining. The goal is to improve the chances of both successful embryo implantation and a safer pregnancy outcome.