Can caffeine harm an unborn baby?

Unlikely. Small amounts of caffeine are probably safe in pregnancy. It's best to limit yourself to less than 200 mg a day, about the amount in two 8 ounce cups of coffee. Large amounts of caffeine, can interfere with your sleep, cause dehydration and stimulate heart rate irregularities. Caffeinated sodas have about 1/3 the caffeine as coffee and tea has about 1/2.