But doctors were split on advising pregnant women on this - some says to quit coffee totally while others say to limit their intake to one cup a day or in moderation.
To straighten out the issue, a team led by Dr. De-Kun Li, a researcher at Kaiser Permanente in Oakland, conducted one of the first studies to take into account morning sickness.
They have concluded that a daily habit of drinking 200 milligrams of caffeine - the amount typically found in just two cups of coffee - significantly increases the risk of miscarriage.
Li said that if a woman becomes pregnant or have any plans of being one, she has to think of quitting to drink any drinks with caffeine, at least for the first trimester when most miscarriage occur.
And that if they really have to drink, they should limit it to one cup of coffee a day.
