Pregnant women should cut out coffee completely to help avoid miscarriage, low birth weight and stillbirth, according to a study of international evidence about caffeine and pregnancy.
In contradiction to official guidance in the UK, US and Europe, there is no safe level for caffeine consumption during pregnancy, according to a peer-reviewed study published in the journal BMJ Evidence-Based Medicine.
It analysed more than 1,200 studies of the drug’s effect on pregnancy and found “persuasive confirmation of increased risk … for at least five major negative pregnancy outcomes: miscarriage, stillbirth, lower birth weight and/or small for gestational age, childhood acute leukaemia, and childhood overweight and obesity.”
But the study was dismissed by the coffee industry, which urged consumers to stick to the public health advice in the UK, US and Europe that daily caffeine intake equivalent to two cups of medium-strength cups of coffee (200mg) is safe for pregnant women.
A large majority of pregnant women consume caffeine, which is also found in energy drinks and at lower levels in cola, chocolate and tea. Britons drink an estimated 104m cups of coffee per day, up from 70m in 2008.
The World Health Organization has acknowledged studies that suggest excess intake of caffeine may be associated with restricted growth, reduced birth weight, preterm birth or stillbirth. It recommends that pregnant women consuming more than 300mg per day should cut back.
The new research by Prof Jack James, of Reykjavik University, found that “current advice … is not consistent with the level of threat indicated by biological plausibility of harm and extensive empirical evidence of actual harm.” It concluded that health recommendations needed “radical revision”.
“The cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine,” the report said.
James said eight out of every nine studies on caffeine and miscarriage reported “significant associations”. Some suggested consumption increased the risk by a third, and others said the risk increased with every extra cup of coffee.
Four out of five observational studies on stillbirth – the loss of an unborn child after 20 weeks – reported increased risk related to caffeine, with the risk increasing by as much as five times in women consuming high doses. Seven out of 10 studies on low birth weight reported a link.
The British Coffee Association, whose members include Costa and Caffè Nero, said James’s study did not establish cause and effect, and it urged pregnant women to stick to existing guidelines.
“The current evidence given by the NHS is based on a comprehensive review of all the scientific evidence available on coffee and health, which shows that pregnant women should limit caffeine intake to 200mg per day or less, and at these levels does not increase the risk of reproductive complications,” said a spokesperson.
“This new study is an observational study, so importantly does not show any direct cause-and-effect link and also is subject to confounding factors such as cigarette smoking and wider dietary issues, which may limit its ability to draw clear conclusions.”
James said causation was likely because of the observed relationships between the amount of caffeine consumed during pregnancy and the risk of negative pregnancy outcomes.
He said the research was notable for the “effort that has been invested in the search for and control of potential confounders”. Variables including body mass, age, pregnancy history, alcohol use and exposure to pollutants had all been considered.
Two years ago the National Institute for Health and Care Excellence in England and Wales updated its advice to urge complete abstinence from alcohol during the first three months of pregnancy because it may be associated with an increased risk of miscarriage.
The Food Standards Agency said: “Based on current scientific opinion, the FSA advises pregnant and breastfeeding women not to have more than 200mg of caffeine over the course of a day, which is roughly two mugs of instant coffee or one mug of filter coffee.”
Public Health England has been contacted for comment.