A new study suggests pregnant women, and those trying to conceive, should avoid drinking coffee and caffeine in general, CNN reports.

What’s happening:

The new study — done at Reykjavik University — found that too much caffeine consumption during pregnancy has been linked to a rise in:

  • Low birthweight
  • Miscarriages
  • Stillbirth
  • Childhood obesity
  • Leukemia

Experts told CNN that 200 milligrams of caffeine — about four cans of Diet Coke — is safe.

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Method:

  • For the study, researcher Jack James analyzed 48 different studies from over the last 20 years. He suggested no amount of coffee is safe for women who are expecting, according to Yahoo News.
  • The study was only observational and did not test for cause and effect, according to CNN.
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  • Andrew Shennan, a professor of obstetrics at King’s College London, in a statement, that “the harmful evidence can, in part, be accounted for by other associated factors that go with high caffeine intake, such as cigarette smoking.”

Why is caffeine bad for children?

Yahoo News explained it like this:

“Caffeine crosses the placenta, exposing a fetus to similar levels to those circulating in the mother’s bloodstream. Unlike adults, developing babies lack the enzyme produced by the liver to break caffeine down.”