Chronic endometritis is chronic inflammation (“itis”) of the endometrium (the uterine lining). Chronic inflammation may hinder normal implantation of an embryo and its subsequent development. A patient with good embryo morphologic quality with either a negative pregnancy or with an early miscarriage may be evaluated for chronic endometritis before proceeding with further treatment.
Evaluation of chronic endometritis is typically a microscopic or histologic diagnosis. A sample of the endometrium is obtained either by an office biopsy or during a hysteroscopy procedure. Under the microscope, the endometrial sample can be stained and analyzed for chronic inflammatory immune cells, known as plasma cells. An endometrial sample full of plasma cells is consistent with chronic endometritis. Vaginal or cervical cultures have shown not to be a reliable indicator of chronic endometritis. In one study of 910 women (J Minim Invasive Gynecol 12(6):514-8), chronic endometritis was found in 30% of infertile women and 35% of cases related to abnormal uterine bleeding.
There are several causes for endometritis; most involve a low grade infection. The cervix or opening to a woman’s uterus usually prevents bacteria from migrating to the endometrial cavity. Intrauterine insemination or embryo transfer catheters bypass the cervical gatekeeper and may introduce infection. If a patient is miscarrying, the cervix may dilate to permit evacuation of the miscarriage tissue but in so doing allow bacterial contamination. Chronic retained products of pregnancy may also be associated with infection.
Treatment consists of removing the source of infection (commonly chronic retained placental tissue) followed by a short course of antibiotics. In some cases, a “proof of cure” repeat endometrial biopsy will be performed after completing antibiotics to ensure a normal endometrium. Empiric use of antibiotics is often used near the time of an embryo transfer to rule out any minimal endometritis during implantation.