Recurrent pregnancy loss is a distressing experience.
Miscarriage is the most common cause of loss during pregnancy, affecting 15-25% of pregnancies. It most commonly occurs at any time within the first 12 weeks of pregnancy.
Of women who are trying to conceive, 1% will experience recurrent pregnancy loss (RPL), or the loss of three or more consecutive pregnancies.
Many risk factors have linked to RPL, but scientists have not yet fully understood the underlying causes.
Researchers at Warwick University in the UK, led by Jan Brosens, professor of obstetrics and gynecology, studied tissue samples from the womb lining of 183 women.
Lack of stem cells in the womb lining of women with RPL
The participants were receiving treatment at the Implantation Research Clinic, University Hospitals Coventry and Warwickshire National Health Service (NHS) Trust in the UK.
Cultures from womb biopsies revealed that there was no epigenetic signature indicating the presence of stem cells, and there were fewer stem cells overall in the women who had been through recurrent miscarriages, compared with a control group.
This lack of stem cells appears to speed up cellular aging in the womb.
Renewal of the womb lining normally occurs with each monthly cycle, after each miscarriage and after a successful birth, but its ability to renew depends on its stem cell population.
In patients with RPL who lack stem cells, there appears to be accelerated aging of the womb tissue. The aging cells mount an inflammatory response, which helps the implantation of an embryo but hinders its subsequent development.
The team concludes that a lack of stem cells, leading to accelerated aging of the lining of the womb, is causing the failure of some pregnancies.
Prof. Brosens explains:
"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. 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."
The next step will be to research a treatment to "correct these defects," which the authors hope could prevent future miscarriages in women who are affected.
Interventions could happen soon
While the authors call for further, longitudinal studies to be carried out, they hope that pilot interventions could start as early as this spring.
Co-author Siobhan Quenby says that future strategies would need to increase the function of stem cells in the womb lining. First, she says, there is a need for new endometrial tests to improve the screening of women who are at risk of recurrent miscarriage.
Quenby then suggests carrying out an endometrial "scratch." This procedure involves superficially scratching the lining of the womb, and it is already used with in vitro fertilization (IVF).
The scratch provokes a "repair reaction," which helps to increase implantation rates.
The researchers believe it can help to increase the number of stem cells in the womb lining.
Last year, Medical News Today reported on results suggesting that progesterone supplements do not help prevent recurrent miscarriage.