I am surprised that your doctor didn't tell you that with your daughter. I had my third in December of 2006, and I was told that I should supplement with Vitamin D drops. It became a recommendation from the AAP sometime between my second(12/04) and third. Apparently they were finding Vitamin D deficiencies in babies that were breastfed, because moms can be deficient in vitamin D, and . Also, the AAP was looking at the world population, which includes all babies including ones that are breastfed by moms in burquas who didn't get a lot of sunlight, moms where there wasn't a lot of sun, and moms and babies with dark skin who didn't produce as much vitamin D from the sun (these were the examples my doctor gave me). Anyway, to make a long story longer, you can supplement, or make sure that you get the baby in sunlight. I did supplement a bit with my third, but not regularly because my first 2 didn't have any problems, and we are outside as much as possible. Here's a link with more info: http://www.kellymom.com/nutrition/vitamins/vitamin-d.html