Immunity is a silent but a salient feature of our body that protects us from foreign substances that are harmful to our health. Immune cells in our body protect us from infection-causing pathogens. Without immunity, we wouldn’t be alive and surviving.
It is thought-provoking how a baby continues to live inside a mother’s body without her immune system attacking it, considering it as a foreign object, at least partially. That being said, a mother’s immunity also has a big role to play in miscarriages. Now, this seems perplexing! To understand this we must know how a woman’s immune works when she is pregnant.
Researchers have always assumed that during pregnancy, the mother’s immune system suppresses to let the baby survive inside her body. However, on the contrary, studies show that the immune system is highly active during pregnancy and in turn, helps in its sustenance and progression.
The immune system helps in all the three significant stages of pregnancy—the implantation, the maintenance and the labor. The scientist came up with something to describe it, it is called ‘an immune clock of the human pregnancy.’ The immune system alters itself during pregnancy to protect the baby from a default attack and simultaneously protects the mother from infections.
The study conducted at the Stanford University, USA, and Ghent University, Belgium found out that the mother’s immune system tunes between three phases—pro-inflammation, anti-inflammation and pro-inflammation again.[ref[Aghaeepour, Nima, Edward A. Ganio, David Mcilwain, Amy S. Tsai, Martha Tingle, Sofie Van Gassen, Dyani K. Gaudilliere et al. “An immune clock of human pregnancy.” Science Immunology 2, no. 15 (2017): eaan2946.[/ref]
At the first stage of implantation, when the embryo attaches to the uterine lining, the cells released by the immune system penetrate into the lining of the uterus and causes inflammation. This inflammation is necessary—without it, the implantation cannot happen. Thus, the immune system is in pro-inflammation phase, which continues throughout the first trimester.
The fetus grows rapidly during the second trimester. As the baby inherits the genetic material from the father, they may produce antigens triggering an immune system response from the mother’s body. To prevent any attack to the fetus, the immune system releases a type of cell called Regulatory T cells also called Tregs, thus creating an anti-inflammation phase that continues till the pregnancy reaches its term.
If the Tregs cells are present in low numbers, mother’s immune system won’t be able to withhold an attack to the fetus thus causing a miscarriage.
Towards the end of pregnancy, the immune system again goes into the pro-inflammation mode, which is when the mothers go into labor—without this switch, the mother won’t go into the labor. If the immune system does not respond normally, a preterm labor or a miscarriage is likely.
Another prime cause of miscarriage is an intrauterine infection. Though the mother’s body can fight away most infections, a viral infection poses a serious threat to the baby. If the mother suffers from a viral infection during her pregnancy, it can lead to fetal inflammation and make them more susceptible to bacterial attacks.
The new discovery not only provides a better understanding of pregnancy, it can help the scientists detect the risk of pregnancy by simply testing the blood sample of the mother and checking the count of Tregs cells. Imagine a simple blood test that could rule out a miscarriage or detect an early abnormality.
For now, this study can provide a better explanation to those women who, most of the times, remain under dark when the doctors are unable to determine the cause behind a miscarriage.