-Dr.Dianne McCallister, Chief Medical Officer at Centura's Porter Adventist Hospital
If you are pregnant, you may want to avoid the second cup of coffee.
A new study from Norway gives more reasons to limit caffeine - associating caffeine with low birth weight - and an increased length of pregnancy.
While obstetricians have been telling pregnant women for years that they should limit their caffeine intake, previous studies looked only at the association between caffeine and premature birth.
This study showed that the birth weight of babies was decreased by one ounce from expected for every 100mg of caffeine - from any source - that the mother consumed.
Beyond that - the researchers found that for every 100mg of caffeine consumed, the length of the pregnancy was associated with a 5 hour increase in the length of the pregnancy.
This study looked at the caffeine from all sources in 60,000 pregnant women in Norway. In addition to the usual sources of caffeine that we consider - coffee, tea and other caffeinated beverages, this study also asked women about caffeine found in such foods as chocolate.
While there is an association that is evident from this study - the study was not set up to show cause and effect.
The current recommendations by the American College of Obstetrics and Gynecology is to limit caffeine to 200 mg a day.
The average cup of coffee - which is a small cup - contains about 90-200 mg of caffeine. A cup of tea, or a chocolate bar, contains about 35 mg.
The best advice is to discuss this with your physician - and be aware of all the sources of caffeine - beyond coffee that you are consuming.
Of course, the safest bet is to obviously avoiding caffeine altogether while you are pregnant.
Dr. McCallister is on 7NEWS at 11 a.m. every Wednesday. If you have a topic or question you would like her to discuss, email email@example.com.