New Study Links Stem Cells and Deficiencies to Multiple Miscarriages

A University of Warwick study has found that most women who have repeated miscarriages have unusually low amounts of stem cells in their uterus linings.

For many women struggling with infertility, repeated miscarriages can be absolutely devastating. Recurrent miscarriages, which are defined as at least three or more consecutive pregnancies that were not carried to full term, happen to one in 100 women. This type of infertility is so heartbreaking because women often do not know what could be causing the miscarriages to happen. New research finds that the underlying cause of this condition may be a stem cell deficiency in the endometrial lining of the uterus.

How Can Stem Cells Affect Pregnancies?

A stem cell is a type of undifferentiated cell that can grow into specific types of cells, such as organ cells or tissue cells. The most well-studied type of stem cell is an embryonic stem cell that is present in an embryo before those cells develop into the specialized cells needed to develop a human body. However, adult humans also have stem cells in their body, and women have human endometrial stromal cells, a specific type of stem cell that exists in the lining of the endometrium. This type of stem cell is used to regenerate the lining of the uterus after each menstrual cycle, miscarriage, or birth. When an embryo is implanted, the stem cell lining of the uterus normally develops into a structure called the decidua, which is used to support the fetus as it grows. In older women, there are typically less of these stromal cells, so it is harder for the body to replace the endometrial lining.

What Were the Findings of This Study?

The study providing new information on this topic is a collaboration between the medical and biology departments of the University of Warwick. 183 women volunteered to participate in the study and donate tissue samples from womb linings. A stem cell normally gives off a unique type of epigenetic signature, but the researchers realized that women who suffered from recent miscarriages did not have this epigenetic signature. Upon further examination, it was discovered that women who had recurrent miscarriages had significantly less stem cells that women who had normal fertility. When the researchers tried to figure out why this was happening, they realized that women with stem cell shortages had prematurely aged uteruses. Because there was not an adequate stem cell amount to refresh the lining of the uterus, women with a stem cell deficiency had a uterus comparable to women much older than them. These prematurely aged uteruses were not able to create a decidua that could support a full term pregnancy. Therefore, the study found that the reason many women have recurrent miscarriages is because their uterus lining is not prepared to support a pregnancy in the first place.

Is There a Way to Prevent Miscarriages Caused by This Deficiency?

Currently, there are a few ways for women with low stem cell counts to successfully carry a pregnancy to term. A few medications may possibly provide a method of increasing stem cell populations. Another useful procedure is an endometrial scratch, which causes a superficial injury to the lining of the uterus. This stimulates a repair reaction that causes more stem cell growth. Now that this study has shown how low stem cell amounts can cause recurrent miscarriages, more research will be done on ways to cure this problem. The researchers of the University of Warwick study hope to develop tests that will easily diagnose low amounts of stem cell types in the uterus. Eventually, more effective drugs and procedures may be found to encourage stem cell growth that will allow embryos to implant in a fully functional endometrial lining.