A new study hypothesizes that preterm labor happens when fetal immune system prematurely sets off its defensive mechanism after mistaking the mother as a possible invader.

The exact cause of preterm labor remains subject to discussions among people in the medical field.

Scientists at the University of California, San Francisco, however, suggest that preterm labor may take place when the fetal immune cells confuse the mother's cells as a threat. This event, akin to a case of "mistaken identity," usually happens when the mother develops an infection that irritates the babies' immune system while still inside the womb.

In this case, the fetal immune system would then attack in the form of inflammatory chemicals that trigger contractions, and then premature labor would happen.

With this new insight, scientists hope that they can subsequently identify biomarkers in the mother's blood that could indicate earlier whether the fetal immune system has already been activated and has been increasing the risk for preterm labor.

Preterm Labor Cause

The unifying principle is that a fetus is yet to develop a mature immune system while still being in the mother's womb. In effect, it should not have significant contribution in pregnancy complications, or so the experts have previously thought.

An analysis of umbilical cord blood that contains fetal cells along with blood taken from women who had healthy pregnancies and those who went into early labor revealed that fetal immune system can actually wake up earlier than expected. Specifically, the fetal immune system wakes up when it detects an infection or inflammation coming from the mother.

This was revealed when scientists conducting the study saw no signs of an immune response in the mother's blood. What they saw instead are two types of immune cells that have been activated in the cord blood of preterm infants. They also found a significant amount of the mother's cells wandering in the cord blood of the preterm infants.

The untimely awakening of the babies' immune system could be a defense mechanism to escape a hostile uterine environment, explains first author Michela Frascoli PhD from the University of Massachusetts Medical School.

Preterm Labor Treatment

Before this study, medicines for preterm labor are aimed at impeding the uterus's early contraction. However, the study suggests that intervening at this point could already be late and futile.

What experts need to do is to detect the moment when the fetal immune system is already awake, most likely weeks before the mother starts feeling the labor pains, explains senior author Tippi MacKenzie, MD, associate professor in the UCSF Division of Pediatric Surgery and the Fetal Treatment Center.

The study is published April 25 in Science Translational Medicine.

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