Answer: I think that you can have a cup of coffee or a coke without thinking twice about it. Studies have shown that very little of the caffeine ingested by nursing mothers appeared in their milk, and the tiny bit that did appear didn’t have any apparent effect on the baby’s heart rate or sleep patterns.
Caffeine is approved by the AAP (American Academy of Pediatrics) for use by nursing mothers. The average cup of coffee contains 100-150 mg of caffeine, so if you drink 5 cups of coffee or less each day, your baby will get less than 3 mg per kg a day. The caffeine peaks in your milk about an hour after you drink the beverage, but the levels are so low that they rarely cause any problems.
Premature babies and newborns eliminate caffeine and other substances from their milk more slowly than older babies, so mothers of tiny babies may want to limit their intake accordingly. Since your baby is nine weeks old and healthy, then I would advise you to enjoy your soda and coffee and cross caffeine off your list of things to worry about.
Anne Smith, IBCLC