Caffeine is the most commonly used psychoactive substance in the world.
Drinking a couple of cups a day is considered to be good for your health - or at least not bad for your health. However, emerging evidence suggests that consuming caffeine during pregnancy may be bad for the baby. The latest study adds to that evidence.
Researchers wanted to know if there is a link between maternal caffeine intake and negative birth outcomes in a population where tea is the main caffeine source.
To do so, they used data from an Irish cohort study. The data, on about 1000 Irish women, provided the usual dietary intakes of caffeinated products during early pregnancy. They then matched the data with hospital records of the women's newborns to get information on the birth size and gestation age at brith.
Tea was the predominant caffeine source (48 percent) followed by coffee (39 percent). The analysis, published in the The American Journal of Clinical Nutrition, showed a consistent link between both coffee and tea caffeine and adverse birth outcomes.
In the highest caffeine consumption group, the risks of delivering babies with abnormally low birth weight or short gestational age at birth were about two times higher. The results were similar regardless of the caffeine source.
While coffee is the main source of caffeine in most parts of the world (about 100mg per cup), it is less recognised that tea contains a significant amount of caffeine, too (about 33mg per cup).
Brewing methods and types of coffee and tea influence their caffeine contests. For example, caffeine content is higher in espresso than instant coffee, and it's higher in black tea than in green tea. So the findings have potentially important public health implications in countries where a lot of black tea is consumed, such as Ireland and the UK.
The recommended caffeine intake level during pregnancy differs across health organisations and countries. The World Health Organisation recommends an intake of less than 300mg per day.
Apart from smaller birth size and shorter gestational duration, maternal caffeine intake has been linked to other negative outcomes for the child, such as a lower IQ. But these findings are from observational studies, and observational studies cannot prove that caffeine cause these outcomes, only that there is a link between them.
Until more definitive evidence emerges, it is prudent to at least limit caffeine intake during pregnancy or when planning to conceive. It is now-well-recognised that tea contains a significant amount of caffeine, so its consumption should also be taken into consideration when trying to adhere to the guideline caffeine intake limit during pregnancy.
