Health Watch -- Labor Signaling

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How does a mother's body know that a baby is ready to be born?

Doctors have long wondered why a woman goes into labor just at the time when the baby is ready to survive in the outside world - and what goes wrong to trigger premature labor. Researchers at UT Southwestern Medical Center at Dallas may have found an answer.

They discovered that the lungs of the developing fetus appear to be what send the signal that starts labor. As the lungs develop, they release a substance called surfactant. This substance is essential for breathing outside the womb. There's a protein within this substance that the fetus "breathes" into the amniotic fluid, where it binds with immune cells called macrophages. These immune cells are activated by the protein, then make their way to the walls of the uterus, where they trigger an inflammatory response that then leads to labor.

The UT Southwestern researchers observed this process in mice. They found that when mice were given the surfactant protein, they went into early labor, while an antibody to the protein led to delayed labor.

This discovery may help doctors understand one possible cause of premature labor. Dr. Carole Mendelson, a UT Southwestern biochemistry and obstetrics researcher, says that women who go into pre-term labor often have an infection in the tissues surrounding the uterus. It's possible that bacteria binding to the macrophages could create a labor trigger similar to that caused by the surfactant protein. The doctors plan more research into understanding labor triggers.

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April 2004

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