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Why the U.S. Gets a "D" in Premature Births, and How That Could Soon Change

By Heather Turgeon |

preterm labor and preterm birth

The mystery of premature labor

Last month, the March of Dimes came out with a report that gave the U.S. a “D” score on preterm births. In this country, 12.3 percent of babies are born prematurely (before 37 weeks) — we’re one of the worst in the developed world when it comes to giving our babies enough womb-time. In Sweden, for example, the rate is around six percent.

Preterm birth is the leading cause of newborn death — which helps explain why the U.S. also has one of the highest infant mortality rates in the developed world.

Babies need at least 39 weeks in the womb – it’s a growing consensus in the medical and public health worlds. Some say we shouldn’t induce for non-medical reasons before 40 weeks, or that we should use ultrasounds to confirm that a baby is in fact 39 weeks (not just go by the due date, calculated by date of last menstrual cycle) before inducing.

But it’s not just elective inductions that hike up our preterm birth rate in this country — premature labor is a major health issue that has long confounded scientists and doctors.

Remember my report last month on the new discovery of what actually triggers the process of labor and childbirth?  It was a major milestone in preterm birth research – here’s a re-cap of the break-through finding:

The exact trigger of contractions and delivery has always been a mystery. But last month, a team of biochemists from the University of Texas Southwestern Medical Center in Dallas used the mouse uterus as a model for childbirth, tracking the expression of certain genes as contractions begin.

The key turned out to be that tiny micro-fragments of RNA (DNA’s single-stranded cousin) in the uterus become extra active at the end of pregnancy. As circulating progesterone levels fall, these miRNA pieces are expressed strongly.

The miRNA affect two important genes, called ZEB1 and ZEB2. These two genes keep labor at bay, because they keep levels of contraction-inducing hormones, like oxytocin, down. Rising miRNA block the two genes, letting oxytocin loose, and labor begins.

Doctors and researchers know that infections and inflammation cause women to go into labor early. So they tested this on mice, inducing labor in some with an infection and others with hormones. Sure enough, the cascade of miRNA and ZEB genes held up. Now scientists know that when a woman gets an infection, the genes and the miRNA likely kick off contractions.

Read the full story about the problem of premature birth, why the U.S. stacks up so poorly with other countries, and how that might soon change.

Image: Babble

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About Heather Turgeon


Heather Turgeon

Heather Turgeon is currently writing the book The Happy Sleeper (Penguin, 2014). She's a therapist-turned-writer who authors the Science of Kids column for Babble. A northeasterner at heart, Heather lives in Los Angeles with her husband and two little ones. Read bio and latest posts → Read Heather's latest posts →

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One thought on “Why the U.S. Gets a "D" in Premature Births, and How That Could Soon Change

  1. Bryan Post says:

    Despite our wealth we also have one of the highest rates of stress per individual in the world. Considering the enormous divorce rates, the alarming amounts of stress, it is no surprise that our mothers are even able to carry us as long as they do.

    Bryan Post

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