Moderate caffeine consumption of about 200 milligrams or 12 ounces of coffee per day didn't appear to increase risk of miscarriage or premature births, a new U.S. review of research concludes. (Dwight Friesen/CBC)

Drinking a cup of coffee a day during pregnancy doesn't seem to cause miscarriage or premature birth, a group of U.S. doctors says.

The opinion appears in the August issue of Obstetrics & Gynecology, a journal published by the American College of Obstetricians and Gynecologists.

For years, women have received mixed messages about the safety of caffeine in pregnancy.

A committee of the college reviewed the latest scientific evidence on large groups of pregnant women and concluded that moderate caffeine consumption — about 200 milligrams or 12 ounces of coffee per day — doesn't significantly increase risk of miscarriage or premature births.

"Given the evidence, we should reassure our pregnant patients and let them know that it's OK to have a cup of coffee," Dr. William Barth, chair of the group's committee on obstetric practice, said in a release Wednesday.

The committee said the evidence was not clear on the pregnancy risks of consuming high levels of caffeine, which would be more than 200 milligrams a day, according to the U.S. group.

Caffeinated tea and pop have less than 50 milligrams of caffeine per serving. The average chocolate bars contain less than 35 milligrams.

The Motherisk Program at Toronto's Hospital for Sick Children currently advises women they don't need to stop drinking coffee during pregnancy, but should avoid overindulging.

For women of childbearing age, Health Canada's recommended maximum daily caffeine intake is no more than 300 milligrams.