The New Nation - Internet Edition

Jennifer Macey

Pregnant women have long been warned of the dangers of drinking, smoking and drug use. But now researchers in the United States say caffeine could be just as harmful.

Research published in the American Journal of Obstetrics and Gynaecology shows that pregnant women who drink two or more cups of coffee or five cans of cola per day are twice as likely to miscarry, compared to women who avoided caffeine altogether.

The study surveyed more than 1,000 women about their caffeine intake during the first two months of their pregnancies.

Irina Pollard is Associate Professor of biological sciences at Macquarie University in Sydney. "Caffeine induces the release of the stress hormones like adrenaline and cortisol and those stress hormones are not good for reproduction," she said.

"This applies to pre-implantation or early pregnancy and also after implementation once the embryo has embedded into the uterus." The research indicates the caffeine crosses into the placenta to the foetus, where it is believed to hinder cell development.

Associate Professor Pollard says pregnant women should treat caffeine as a drug.

"In the pre-conception period when people want to become pregnant, it affects sperm as much [as] the early pregnancy in a woman as well," she said.

"So it would be a good idea to reduce or try and cut out on all caffeine-containing beverages, food like chocolate, and of course, other drugs, alcohol and things like that."

One in six Australian women will have a miscarriage but the exact causes are still unclear.

Professor Michael Chapman heads the School of Women's and Children's Health at the University of New South Wales.

He agrees that caffeine should only be taken in moderation during pregnancy. However, says other lifestyle factors such as age, drinking and smoking may also have an impact on miscarriage rates.

"Excessive coffee drinkers tend to be people who are highly stressed, and certainly stress has a relationship with miscarriage and so that's one aspect that they haven't looked at," he said.

"It was also interesting that also published this week in Epidemiology, which is another journal, an American study concluded that there isn't a relationship with caffeine.

"So, I thinkt it's still an open question."

Professor Chapman says he won't be changing his dietary advice to his patients.

"I certainly say to my patients, a couple of cups of coffee a day is probably no problem," he said.

"If you go more than that, certainly the evidence is there enough to cause doubt, and at a time when everybody is worried about their pregnancy, restricting coffee intake for most people should be quite a feasible thing to do."

-ABC News