Study: Fetuses Can Wake Up In the Womb

Study complicates the debate about when life begins.

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The debate about when life starts just got a little more complicated—a new study suggests that human fetuses might be able to "wake up" in response to certain sounds while still in the womb.

According to Evan Balaban, a researcher at McGill University in Montreal and author of the study, a fetus' brain might be developed enough to wake up about seven months into a pregnancy. The fact that babies can likely wake up in the womb might explain previous studies that found that infants as young as one day old react more strongly to their maternal language versus foreign languages.

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"There's been a lot of disagreement about whether embryos ever wake up before they're born, and the scientific consensus is that they don't," Balaban says. "It seems like things that are extremely interesting to them can wake their brains up."

Balaban studied the development cycles of embryonic chickens to make the discovery—chicks have long been used to study fetal development because they go through many of the same stages as humans. Using X-ray imaging, Balaban discovered that the developing chicks' brains responded to their mothers' calls—other, unrelated sounds didn't stir their brains. Balaban says he believes in humans, a mother's voice might wake up a fetus—now researchers just have to find out if other noises do the same.

The finding opens up questions about whether babies can learn before they're born and whether harm can be done if a fetus is "woken up" and exposed to harsh noises, he says.

"We have no idea what happens if things from the outside world are affecting fetuses—is it a good thing or bad thing?," he says. "Maybe it doesn't matter."

To determine if playing certain sounds has an effect on learning or development, Balaban says chickens can also be used. In future studies, he plans to test whether artificially waking up chicken embryos improves or limits their cognitive development.

That question is especially important for babies who are born prematurely because hospitals would be able to build a care unit environment that best speeds up brain development.

"A lot of times, prematurely-born infants' brains are still developing, but it's one of the things we don't understand very well," he says. "There's all these last-minute connections being made [in the brain], but we have no idea if the outside world is influencing that."

Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at