Here's How Many Calories It Actually Takes to Grow a Baby

Anyone who’s had a baby knows that it takes a great deal of extra energy. (Just ask your swollen feet and aching back at the end of a long day.) But in a recent study published in Science, scientists say that pregnancy demands even more energy than they previously thought: 50,000 dietary calories over the course of nine months, to be exact.

Dustin Marshall, an evolutionary biologist at Monash University in Australia, told The New York Times that previous estimates were lower because scientists typically assumed that most of the energy involved in reproduction ended up stored in the fetus. But they’ve since discovered that only 4 percent of the total energy costs of pregnancy is stored in baby’s tissues—the other 96 percent is required to run the mom-to-be or pregnant person’s body.

“The baby itself becomes a rounding error,” Marshall said. “It took us a while to wrap our heads around that.”

There’s no word on whether these findings will affect healthcare providers’ recommendations. Currently, the American College of Obstetricians and Gynecologists (ACOG) recommends eating about 340 extra calories a day during the second and third trimesters as part of a healthy pregnancy diet—although, keep in mind that calorie needs are highly individualized. One thing’s for sure: You’ll need a lot of extra fuel.