Recurrent miscarriage is typically defined as having three or more miscarriages in a row, whether or not you have had any healthy pregnancies. If this has happened to you, you’re undoubtedly looking into the possible causes of recurrent miscarriages. We turned to Dr. Daniel E. Stein, Medical Director with WINFertility, for answers.
Abnormalities of the uterus play a significant role in impaired fertility and increased miscarriage rates. Women with recurrent pregnancy loss (RPL) should see a board-certified reproductive endocrinologist and undergo a thorough diagnostic evaluation that includes an assessment of the uterus and pelvis.
Genetic abnormalities in embryos are the primary cause of single miscarriages and likely recurrent miscarriages. Non-genetic factors, however, also contribute to RPL. Anatomical defects of the uterus are common and account for 10%-20% of RPL.
Uterine abnormalities can be diagnosed using a variety of tools including pelvic ultrasound, saline hysterosonography, hysterosalpingography, and hysteroscopy.
- During a saline hysterosonogram, saline is injected through the cervix into the uterus in order to better visualize the uterine cavity during ultrasound.
- During a hysterosalpingogram, a special dye is injected into the uterus to allow X-ray detection of uterine and fallopian tube abnormalities.
- Hysteroscopy involves the introduction of a thin telescope through the cervix into the uterus to directly visualize the uterine cavity and surgically correct intrauterine abnormalities.
MRI scans can help diagnose complex uterine abnormalities, and laparoscopy, direct telescopic visualization of the pelvic organs through small skin incisions, is used in some cases for both diagnosis and treatment.
Here are four of the most common uterine abnormalities that may be causing your miscarriage.
Fibroids
Fibroids are the most common acquired uterine abnormality in women of all races. They develop in 30%-60% of non-black women and up to 80% of black women during their lifetimes.
Fibroids are smooth muscle tumors that are non-cancerous in more than 99% of cases. They vary from a few millimeters to several centimeters. They may be located within the uterine cavity, the uterine muscle wall, or outer wall and surface of the uterus. Fibroids located within the uterine cavity, and some within the uterine muscle wall, often lead to miscarriages and even adversely affect fertility.
The operation to remove fibroids is called a myomectomy. Fibroids can be removed from within the uterine cavity using hysteroscopy. This procedure can enhance fertility rates and reduce miscarriage rates. Removal of fibroids outside the uterine cavity has not been found to consistently reduce miscarriage rates but might be effective to reduce heavy menstrual bleeding or pain.
Congenital Abnormalities
During pregnancy, multiple congenital abnormalities may occur. These abnormalities can lead to the development of only a portion of the uterus (unicornuate uterus), a double uterus (didelphic uterus), or a uterus that fails to fuse properly (bicornuate uterus). The most common congenital uterine abnormality, however, is the uterine septum, a condition in which incomplete development leaves a wall of solid tissue within the uterine cavity. This solid tissue wall has a poorer blood supply than normal uterine tissue, contributing to the increased rate of miscarriages and preterm labor.
Approximately 0.5% to 1% of women have congenital uterine abnormalities, but the prevalence may exceed 15% in women with RPL.
Polyps
Polyps are benign growths within the uterine cavity that can induce inflammation and bleeding. Like fibroids, polyps grow in response to reproductive hormones and range in size from a few millimeters to a few centimeters. An association between polyps, infertility and miscarriages has been reported, but studies have not yet determined if polyps cause infertility or miscarriage, and it is not clear that removing polyps (polypectomy) reduces miscarriages. Polypectomy is generally performed by hysteroscopy.
Scar Tissue
Intrauterine adhesions, or scar tissue, result from infections, miscarriages, abortions, or other types of uterine surgery. They can affect a small part of the uterine cavity, or involve the entire surface leading to loss of periods and infertility. The incidence of adhesions in women with RPL has been reported to be higher than in women with successful pregnancies, but the contribution of scar tissue to RPL is still unclear.
Removing adhesions (adhesiolysis) is performed using hysteroscopy and microscissors. Some women regain their periods after this surgery but it is unclear that miscarriage rates are reduced.
About the Author
Dr. Daniel E. Stein is a Medical Director with WINFertility, the nation’s leading fertility benefits management company. He is also the Director of RMA of New York’s Westside office and is Chief of Reproductive Endocrinology at Mount Sinai West Hospital. Dr. Stein is board-certified in both obstetrics and gynecology and reproductive endocrinology and infertility.