Too Much Caffeine During Pregnancy Could Have a Surprising Effect on Baby

If you cherish the 200 milligrams of caffeine per day that’s generally said to be safe during pregnancy , don’t worry; you’re still in the clear. But a new study is examining how different levels of caffeine during pregnancy can affect baby, and straying into higher levels can lead to higher weights throughout baby’s first year.

Researchers from the Norwegian Institute of Public Health looked at data from over 50,000 women who participated in the Norwegian Mother and Child Cohort Study between 1999 and 2008. They categorized women based on their reported caffeine consumption: low (0-49 milligrams per day), average (50-199 milligrams per day), high (200-299 milligrams per day) or very high (300 or more milligrams per day). Women who fell into the “very high” range raised infants with a 66 percent higher risk of “excess growth” during the first year, meaning they were in the 75th percentile for their age . Their risk of being overweight lasted through age 8.

Just how much coffee would constitute 300+ milligrams of caffeine per day? It depends on how you make your coffee, but a standard 12-ounce cup has about 200 milligrams. And of course, caffeine can come from other sources, like tea, soda and candy.

Women who fell into the “average” and “high” groups did appear to still be slightly affected by caffeine, raising kids with 10 percent and 30 percent higher risks, respectively, of excess growth.

A caveat: The women surveyed were only asked to record their caffeine intake once, at 22 weeks of pregnancy. So there’s not a ton of consistent data to draw conclusions from. But it’s enough to support existing recommendations of limiting your caffeine intake to 200 milligrams or less. Remember, when you load up on caffeine, baby does too, because it crosses the placenta. That jolt is stronger to her system—and heart rate—than yours.