Causes of Miscarriage, a Multipart Series
Part II structural abnormalities of the uterus
People are often surprised to learn that between 20 and 50% of all pregnancies end in miscarriage. The majority of these losses occur early in the pregnancy, many before a woman even knows that she is pregnant. Most of these losses are due to random, one time, chromosomal errors in the embryonic DNA. Fortunately, such errors are unlikely to repeat and therefore, most women do not experience multiple miscarriages.
Amongst those women who do experience multiple miscarriages, a variety of causes should be explored. One potential cause for recurrent miscarriages is a structural abnormality of the uterus.
The uterus, or womb, is a highly functional, dynamic and resilient organ. To visualize, it can be thought of as an empty 3 walled room with all surfaces completely covered by a lush shag carpet. The room has 2 small openings at 2 of its corners where the fallopian tubes enter, and a one larger opening at the third corner which is the cervix.
The contour and lining of the cavity are critically important for implantation and continued gestation. If the contour is disrupted or the lining inadequate, the uterus may be less receptive, and an embryo may not be able to implant, or may stop growing after implantation. Amongst the causes of this decreased receptivity are:
1. Uterine septum- a septum is a remnant of tissue, leftover from the embryonic formation of the uterus. It can be visualized as a small wedge emanating from the top of the uterus. In addition to taking up valuable space inside the uterus, the tissue has a poor blood supply. This means that any embryos which implant within the vicinity of the septum will not be able to obtain the nourishment they need. Eventually, this increases the chance for miscarriage.
2. Uterine fibroids- Fibroids are benign muscular tumors that are very common. Up to 50% of all women have at least 1 fibroid. Most fibroids do not cause any problems with reproduction. However, if a fibroid is protruding into the uterine cavity, it can disrupt implantation or continued gestation.
3. Polyp- A polyp is a soft rounded piece of tissue which emanates from the endometrial lining. The vast majorities of polyps are benign, but can potentially be detrimental to an embryo due to either physical disruption or through inflammation.
4. Scarring- Scarring inside the uterus, is different than most people’s perception of scarring. Within in the uterus, a scars typically extend between two or more walls, this condition is sometimes called Asherman's syndrome. The scar tissue distorts the space within the cavity and prevents proper implantation. Scarring usually occurs following uterine surgeries such as D and C’s, miscarriages, or infections.
Fortunately, each of these issues is surgically correctable. Using a long thin camera equipped with an operative port, called a hysteroscope, any of the above abnormalities can be identified and repaired. Theses surgeries are all minor procedures which take less than an hour and require minimal recovery time. Most importantly, they may reduce the risk for another miscarriage significantly.
If you have questions about miscarriage or any fertility treatment in general, feel free to contact us, we’d be happy to chat with you.