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Physical Causes of Recurrent Pregnancy

Physical causes of recurrent pregnancy loss include uterine abnormalities, scar issue and fibroids

All healthy pregnancies attach to and grow within the uterine cavity.  Unfortunately, some women are born with a uterus that did not form normally. Having a uterine or tubal abnormality will likely lead to recurrent pregnancy loss.

It appears that approximately 5% of fertile women have uterine anomalies, and despite their abnormally shaped uterus, they were still able to successfully conceive and deliver a child. On the other hand, approximately 15% of patients with recurrent pregnancy loss have an abnormal uterus.

Uterine abnormalities: a leading cause of recurrent pregnancy loss

When a woman is a fetus developing in her mother’s uterus, she initially has two separate uteruses (“uteri”), each originating near the corresponding kidney.  As the female fetus develops, these two early uteruses migrate towards each other and eventually fuse.

Ideally, the wall between the two separate uteruses reabsorbs, resulting in a normal, single, triangular shaped uterine cavity.  Anatomical abnormalities result when this sequence of events does not occur or fails to occur completely.

Many women experience infertility as a first sign of a uterine abnormality.

Septate Uterus: In a large study from Yale, 85% of patients with a septate uterus either failed to conceive or miscarried repeatedly. Following repair of this most common uterine abnormality, 88% of patients went on to deliver successfully while only 12% continued to have difficulty – either they failed to conceive or they continued to miscarry.

Other presentations of far less common uterine abnormalities are listed below. Surgical correction does not appear to improve the prognosis in patients with these anatomic barriers to pregnancy:

Bicornuate Uterus: This results in having separate uterine cavities sharing a single cervix.

Unicornuate Uterus: Only one of the fetal uteri develops.

Complete Uterine Duplication: Two uterine cavities, each with its own cervix, can support a pregnancy, but it is unlikely to occur.

Uterine scar tissue

Another uterine abnormality that can interfere with successful conception is the presence of scar tissue within the uterine cavity. This typically results following a D&C if too much uterine lining tissue is removed – the walls of the uterus can subsequently stick together, making the cavity small and irregular.

Additional anatomic abnormalities

Other causes of recurrent pregnancy loss include uterine fibroids or endometrial polyps. Either of these conditions can cause abnormal uterine bleeding or they may be asymptomatic.

Fibroids are benign tumors caused by an overgrowth of uterine muscular tissue. They can occur inside the uterine cavity, in the muscular wall of the uterus, or on the outside of the uterus. Fibroids may also cause a significant increase in menstrual cramps, pelvic pressure, or pelvic pain.

Polyps are an overgrowth of glandular tissue within the uterus.

A pelvic exam or in-office procedure called a hysteroscopy can reveal anatomical causes of recurrent pregnancy loss. Please contact Texas Fertility Center to schedule a consultation with a reproductive endocrinologist who specializes in restoring fertility.