Drinking two cups of coffee a day during pregnancy can double the risk of miscarriage for expectant mothers, researchers say.

A US study has confirmed that high doses of caffeine during pregnancy, from coffee, tea, caffeinated soft drinks or hot chocolate, can increase the risk of losing a baby.

Women who consumed 200 mg or more of caffeine per day – equivalent to two or more cups of regular coffee or five cans of cola – had twice the miscarriage risk of women who consumed no caffeine, the study found. Even those who consumed less than 200 mg of caffeine daily had a more than 40 per cent increased risk, the study, published in the American Journal of Obstetrics and Gynecology says.

Caffeine is known to cross through the placenta from mother to the foetus, and is thought to influence cell development and decrease blood flow, causing harm to the developing child. Current guidelines from the Food Standards Agency recommend 300 mg of caffeine a day as the safe upper limit for pregnant women.

Experts said the new findings would prompt them to advise women to cut out caffeine altogether, at least for the first 12 weeks of pregnancy.

Miscarriage occurs in about one in six confirmed pregnancies, usually within 12 weeks, when the foetus is especially vulnerable. While previous research showed a link between high caffeine consumption and increased risk of miscarriage and stillbirth, this is the first study to take fully into account morning sickness, which causes many pregnant women to avoid caffeine and cut down their intake.

It examined data on 1,063 pregnant women in San Francisco from October 1996 to October 1998 who did not change their pattern of caffeine consumption during pregnancy. Women in the study were asked about the amount and frequency of their intake of caffeinated beverages. Pregnancy outcomes up to 20 weeks of gestation were determined for all participants.

Overall, 172 of women in the study (16.18 per cent) miscarried. Whereas 264 women reported no consumption of any drinks containing caffeine during pregnancy, 635 women (60 per cent) reported consuming between 0-200 mg of caffeine a day, and 164 women drank 200 mg or more. Other risk factors for miscarriage were also accounted for in the study, which found that miscarriage was associated with consumption of caffeine overall, rather than particular drinks.

DeKun Li, who led the study for Kaiser Permanente, a US health insurance company, said: “This strengthens the association between caffeine and miscarriage risk because it removes speculation that the association was due to reduced caffeine intake by healthy pregnant women.

“The main message for pregnant women is that they probably should consider stopping caffeine consumption during pregnancy.”

Pat O’Brien, a consultant obstetrician at University College Hospital, London, and spokesman for the Royal College of Obstetricians and Gynaecol-ogists, said: “This is the best evidence we now have on the subject and I will advise patients to avoid caffeine completely, at least for the first 12 weeks of pregnancy. Good studies have shown it may be safer to drink caffeine after that, but no more than 200 mg a day is still to be recommended.”

Caffeine doses
stimated caffeine in a 150ml drink:

100mg in coffee
39mg in tea
15mg in a caffeinated soft drink such as cola
2mg in hot chocolate
2mg in decaffeinated coffee

Source: American Journal of Obstetrics and Gynecology

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