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How the immune system acts during pregnancy

A nurse cares for a premature baby (M. Spencer Green / AP)

A woman's immune system balances two jobs during pregnancy: preventing itself from attacking the fetus as it would foreign tissue and keeping the mother safe from infection herself. Disruptions to this balance can cause a host of complications for the pregnancy, namely delivery at 34 weeks — six weeks sooner than what is considered normal and healthy. In the U.S., 10–12% of babies are born before full term.

Stanford researchers have detailed what this balance (referred to as the "immune clock") should look like in a pregnancy in which the baby is delivered at term, per a new study.

Why it matters: "Once you understand what is normal…you can understand what is abnormal," Brice Gaudilliere, one of the researchers, told Axios. With the model "immune clock" on hand, doctors may be able to predict whether a woman will deliver preterm by observing if that clock is ticking too slow or too fast.

How it works: The researchers looked at blood samples from patients at three points during their pregnancies and six weeks after giving birth. They counted the types of immune cells present and analyzed how the individual cells and networks of signaling pathways reacted to bacteria.

They found pregnant women's immune systems change on a strict, universal schedule:

  • The adaptive immune system, which consists of antibodies and white blood cells that learn to fight pathogens, recedes.
  • The innate immune system, which is the body's set of ingrained defense mechanisms, such as inflammation at the site of an infection, picks up the slack.

What's next: One goal is to predict the timing of labor with the "immune clock," which Gaudilliere says is already underway in their lab. They're also trying to figure out what makes immune cells deviate from normal in women who deliver preterm. Nima Aghaeepour, another researcher on the study, told Axios they hope this insight will be able to teach those cells how to fix themselves — similar to the CAR-T cancer therapy approved by the FDA earlier this week.

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