A study currently underway at the University of Leeds, UK, is trying to narrow in on an exact measure for harmful caffeine intake during pregnancy based on an expectant mother's metabolism for caffeine.
"Caffeine is present in many products from chocolate to over-the-counter medications such as flu remedies," said Dr Sara Kirk from the University's Nutritional Epidemiology Group, making it difficult "to measure a person's caffeine intake as caffeine levels in drinks vary from one cup of coffee or tea to another".
The project is working on the assumption that the ability to breakdown caffeine varies between individuals. It is investigating the correlation between caffeine intake and caffeine metabolism during pregnancy and the risk of having a low birth-weight baby.
To date research suggests that too much caffeine during pregnancy - over five cups of ordinary strength coffee a day - could increase the risk of having a low birth-weight baby.
But caffeine is found in more sources than just coffee and the University of Leeds study wants to shed light on what advice should be given to pregnant women on caffeine intake. "We hope it will clarify the role of caffeine in pregnancy and inform health professionals working with pregnant women," said project leader professor Janet Cade.
While scientific research has pointed to the negative effects of excessive caffeine consumption during pregnancy, caffeine has been used for 25 years to help alleviate apnea of prematurity, a condition in which premature infants stop breathing for 15 to 20 seconds during sleep.
A study from McMaster University in Hamilton, Ontario, published in The New England Journal of Medicine saw that intravenous caffeine reduced the rate of bronchopulmonary dysplasia, a chronic lung disease of babies, by 37 percent (an odds ratio of 0.63) in a group of infants with very low birth weight.
The McMaster research team, under Dr Barbara Schmidt, observed the condition of 2006 very low birth weight infants randomly given intravenous infusions of caffeine or a placebo for their first 10 days of life until their breathing conditions improved.
They observed that the caffeine reduced the rate of bronchopulmonary dysplasia developing in the infants - a disease that can manifest itself after very premature birth or use of a breathing machine.
Except for a temporary reduction in weight gain, the study found that caffeine has no apparent short-term risks. However the researchers said there is "insufficient" information to conclude potential long-term effects of caffeine therapy on premature babies. The team is currently continuing research on these effects.
"Follow-up of our study cohort to the corrected ages of 18 to 21 months and 5 years, currently in progress, is needed before one can confidently recommend the standard use of methylxanthine therapy for apnea of prematurity," wrote the authors.