Experiencing one miscarriage is devastating enough, but for some women it happens again and again. Medical experts haven't been able to make a connection as to why some women experience multiple miscarriages, but researchers from the University of Warwick think they have the answer.
Professor Jan Brosens and his team discovered that a lack of stem cells in the womb lining is likely responsible for miscarriages in "thousands" of women.
"We have discovered that the lining of the womb in the recurrent miscarriage patients we studied is already defective before pregnancy," the professor of obstetrics and gynecology wrote in the study, published in the journal Stem Cells in 2016.
For the study, Brosens and his team studied tissue samples from the womb linings donated by 183 women being treated at the Implantation Research Clinic, University Hospitals Coventry and Warwickshire NHS Trust. They found that an "epigenetic signature" common with stem cells was missing from the tissues of women who have suffered more than one miscarriage.
Their findings are notable because although miscarriage is relatively common—between 15 and 25 percent of pregnancies end this way—only one in 100 women trying to conceive suffer three or more consecutive pregnancy losses.
The team also found that a lack of stem cells increases the aging rate of cells in the womb. The uterus relies on stem cells to regenerate after menstruation, pregnancy and miscarriage; the lack of those cells—and the aging process—creates an inflammatory response that affects the ability for a fetus to grow to full term.
"After an embryo has implanted, the lining of the uterus develops into a specialized structure called the decidua, and this process can be replicated when cells from the uterus are cultured in the lab," wrote Brosens. "Cultured cells from women who had had three or more consecutive miscarriages showed that aging cells in the lining of the womb don't have the ability to prepare adequately for pregnancy."
In other words, the body can't fully renew itself to make a welcoming environment for a baby.
While this research paints a bleak picture, there is hope. The team believes that this discovery will lead to treatments that will stimulate the function of stem cells in women without them—and they're already working on new interventions.
"Our focus will be two-fold," said Siobhan Quenby, study co-author and University of Warwick Professor of Obstetrics. First, they'll work to improve how at-risk women are screened through new endometrial tests.
"Second, there are a number of drugs and other interventions, such as endometrial 'scratch', a procedure used to help embryos implant more successfully, that have the potential to increase the stem cell populations in the womb lining."
Added Brosens: "I can envisage that we will be able to correct these defects before the patient tries to achieve another pregnancy. In fact, this may be the only way to really prevent miscarriages in these cases."