Dr. Greene's Answer
Babies can experience many stool changes during the first eight weeks or so. First are the days of slow, sticky, meconium stools, but by the end of the first week, stooling speeds up and breastfed kids have a stool every time they eat–or even more often. They average 8 to 10 soft, yellow, seedy stools.
Over the next three weeks, in breastfed kids, this number usually starts to drop. By 4 weeks, the average is about four soft stools a day, though there is quite a lot of variability in this. At 8 weeks, the number drops to an average of only one a day and some breastfed babies have only one every several days–up to once every seven days or so can be normal.
If your baby is suffering from diarrhea, our biggest concern is dehydration. We want to be sure that kids are getting in plenty of fluid to replace what is lost, and then some. If you were to notice yourself becoming engorged, or if you notice that your baby is not making at least one wet diaper every eight hours or is suffering from a fever, dry mouth, or dry mucous membranes, you want her to be seen right away. It is also important that your baby continues to gain adequate amounts of weight. If she isn’t, your doctor may suggest some tests, supplementing with formula, or pumping to increase your breast milk supply. Otherwise, this type of stooling could come from developmental changes in the intestines or from a mild virus. It could also be a reaction to a food in your diet (the most common of these is to milk). Let your pediatrician know about the stools in a phone call or at your baby’s 1-month checkup.