I agree with all the information given above, but after trying everything available (La Leche, lactation consultant, etc), I was never able to nurse exclusively. I had a very laid back doctor with my first child and he kept telling me not to worry about the lack of weight gain. At one month, we went to a different doctor for a second opinion. To make a long story short my son was almost labeled failure to thrive which can lead to social services involvement. We started supplementing immediately and he quickly gained weight and then stabilized his weight. I was slightly more successful with my following two, but both required supplements. I definitely would continue to nurse as long as possible even if you have to supplement since you are providing important nutrients and immunity to your child. It was very difficult not to view this as a failure, but even my friends at the La Leche mothers group agreed it was the only responsible decision. It is a good thing I was not a pioneering woman - three c-sections, gestational diabetes and unsuccessful breastfeeding would have been very difficult to overcome without modern medicine. Good luck!