A Danish study has concluded that pregnant women who drink moderate amounts of coffee every day are not increasing the risk to their baby.
The research is published in the British Medical Journal.
The study was conducted because some research has suggested that caffeine intake during pregnancy is linked to increased risk of lower birth weight and premature births, but there are doubts, and there is a lack of evidence from randomized controlled trials.
However, this randomized, double-blind controlled trial could find no significant difference between drinking moderate amounts of caffeinated and decaffeinated coffee in terms of adverse outcomes such as birth weight and size and premature birth.
The research team of four scientists was based at the University of Aarhus in Denmark, and was led by Assistant Professor Bodil Hammer Bech from the University’s Institute of Public Health, Department of Epidemiology.
The scientists recruited 1207 pregnant women who had been drinking at least 3 cups of coffee a day and who were less than 20 weeks pregnant at the start of the study. They randomly assigned approximately half the women to the caffeinated group and half to the decaffeinated group.
For the rest of their pregnancy the caffeinated group were given instant caffeinated coffee to take home and drink, while the decaffeinated group were given instant decaffeinated coffee. Neither the women nor the researchers who gave out the coffee knew which was which. There was a small fallout rate of women who did not complete the trial and some of the women who were on decaffeinated coffee guessed which one they were on.
The women were interviewed on a regular basis to find out what they were taking every day that could contain caffeine. Some of the women drinking decaffeinated coffee also consumed products (such as tea, chocolate and cola drinks) that had caffeine in them. However the researchers maintain that their results stand up because the differences between the two groups came to an average of 182 mg of caffeine a day, which is the level at which other studies maintain adverse birth outcomes are likely to occur.
The length of the pregnancy term and the birthweight and measures of baby’s size were recorded for each woman who stayed with the trial.
The women’s age, weight pre-pregancy and their smoking habits were also factored in.
The results showed there was no significant statistical difference between the two groups in terms of the length of the pregnancy and the size of the babies.
Of the babies born to the caffeinated group, 4.2 per cent of them were premature, and 4.5 per cent were smaller than usual for the length of the pregnancy. Of the babies born to the decaffeinated group, 5.2 per cent of them were premature and 4.7 per cent of them were smaller than normal for their gestation term.
Asst Prof Bech said that they found no overall significant effect on the birthweight or gestational age of babies born to mothers who had moderate caffeine intake during the second half of their pregnancy. The researchers emphasized that any effects in the first half of pregnancy would not be detected by this study.
However, when they analyzed the results for the smokers in the two groups they found a slight lowering of birthweight of babies born to smokers who did take caffeine.
The UK’s Food Standards Agency advises pregnant mothers to limit their daily caffeine intake to 300 mg a day. They say that “If you eat a bar of plain chocolate and drink 3 cups of tea, a can of cola and a cup of instant coffee in a day, you’ll have reached your 300mg limit”. They also advise women to read food and medicine labels as caffeine could be an unexpected added ingredient.
“Effect of reducing caffeine intake on birth weight and length of gestation: randomised controlled trial.
Bodil Hammer Bech, Carsten Obel, Tine Brink Henriksen, Jørn Olsen.
BMJ, doi:10.1136/bmj.39062.520648.BE (published 26 January 2007)
Advice on caffeine and other foods for pregnant women from the Food Standards Agency (UK).
Written by: Catharine Paddock
Writer: Medical News Today