When will labor start? This might be the signal

During the last few weeks of pregnancy, many women keep an overnight bag ready to go to the hospital at a moment’s notice — just in case labor suddenly begins.

Late in pregnancy, women are on perpetual alert because there is no clear signal that labor is about to start — well, not that experts have been able to tell so far, anyhow. But it’s about more than convenience: Understanding the mechanisms that initiate childbirth are especially important when treating women at risk of going into labor early.

childbirth hospital mom with baby

Uncovering the signal for when labor is about to begin

“The initiation of the birthing process is complex. Several body systems maintain pregnancy through a delicate balance — altering this balance tends to promote labor,” said lead author Ramkumar Menon, assistant professor in the The University of Texas Medical Branch at Galveston department of obstetrics and gynecology.

Researchers from UTMB have uncovered a cellular signal in the amniotic fluid around the fetus that builds up when a pregnant woman is about to go into labor.

The UTMB team focused their investigation on telomeres, which are the parts of the DNA that protect our genetic data while cells are dividing.

These telomeres become shorter every time a cell divides, which hinders their ability to ensure that the new cells are identical to the parent cells. This shortening process is linked with the changes that take place in our bodies as we age. Over time, the telomeres become too short for the cell to divide and they become “senescent.”

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“We investigated whether the presence of senescent telomere fragments in the amniotic fluid around the fetus is linked with labor status, as we know that the telomeres continue to get shorter as the pregnancy progresses,” Menon said. The findings were published in PLOS ONE.

Amniotic fluid studied for DNA links to birth

The researchers used amniotic fluid samples from the Nashville Birth Cohort Biobank of 50 women in labor, and 51 women at the end of their pregnancy but not in yet in labor. They also acquired demographic information from patient interviews and medical information from their medical records. In addition, the team dissected fetal membranes from the placenta after babies were delivered at term.

Menon said his team wanted to know what triggered a change in the delicate balance that had maintained a pregnancy. “We began this study suspecting that that the senescent cells cause oxidative stress-associated damages to the amniotic sac that create inflammation in the placenta,” said Menon. “We know from previous studies that inflammation can alter the balance of the mother’s hormones in the uterus, triggering the labor process.”

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The researchers used telomere mimics, resembling those found in amniotic fluid, and conducted cellular analyses, finding more telomere fragments when a woman who was in labor compared to women who were at the end of their pregnancy but not yet in labor.

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They report that as the fetus mature in the womb and nears term, placenta and other related tissues also age correspondingly due to telomere fragmentation and eventual loss. These telomere fragments can increase sterile inflammation, as Menon termed, potentially signaling fetal maturity to trigger the process of labor and eventual delivery.

“A better understanding of the pathways activated by telomere fragments and their contribution to fetal membrane senescence may contribute to the design of more effective labor assessment, perhaps including preterm birth risk and direct medical interventions for labor induction or prevention.”

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