Most people are quick to agree that pregnant women should cut caffeine out of their diets. But current research has shown that a moderate intake of caffeine won't do any harm to developing fetus. Moderate intake would equal approximately 3 cups of coffee per day (300-400mg of caffeine). Of course, you can't forget to count the hidden caffeine in soft drinks and some over-the-counter medications. Check here to see the caffeine content in your favourite drinks.
Past studies of caffeine and pregnancy have pointed to all manner of problems, such as stillbirths, heart defects and other congenital problems. But further examination of these studies shows that other lifestyle and environmental factors (such as smoking or poor eating habits) were not properly taken into account.
Caffeine is a stimulant, and an addictive one at that. It has the same effect on your baby as it does on you. If nothing else, high caffeine intake during pregnancy will create an addiction in your child and force them to suffer withdrawal symptoms once they are born. Some studies have also shown a higher rate of miscarriage and low birth weight babies when the mother has had more than the 'moderate' amount of caffeine mentioned above.
Herbal teas are a safer haven, with respect to caffeine intake. But not all herbs should be consumed while pregnant. Herbs such as ephedra, mugwort, and cohosh should be avoided. Here is a full list of herbs to avoid. Stick to safer herbs such as mint, chamomile, or fruit teas.
Overall, my advice would be to try and cut your coffee or tea intake to no more than one or two cups a day. Removing all caffeine would be the safest route, but don't stress yourself over it if you feel you just have to have a cup to get going in the mornings. Oh, and don't forget some of the caffeine-free coffee substitutes on the market, like chicory.
A bit of irony...
My wife cut out pretty much all coffee and tea throughout her pregnancy to be on the safe side. As it turns out, Emily was born 2 months premature anyway, and guess what was part of her medical care while in the NICU? Yep, that's right. Caffeine. She got daily caffeine shots to help stimulate her breathing and her heart rate.