Why not just supplement the baby until mom's vitamin D status is improved? From Nutrition During Lactation, Institute of Medicine, 1991. "In summary , exclusive breastfeeding results in normal infant bone mineral content when maternal vitamin D status is adequate and the infant is regularly exposed to sunlight. If the infant or mother is not exposed regularly to sunlight, or if the mother's intake of viatin D is low, supplements for the infant may be indicated (5 - 7.5 ug/day)." Also from same reference: "Breastfed infants require approximately 30 minutes of exposure to sunlight per week if wearing only a diaper, or 2 hours per week if full clotherd without a hat to maintain normal serum 25-hydroxycholecalciferol levels. Darkly pigmented infants require a greaster exposure to sunshine to initiate the sysntheseis of vitamin D in the skin." See the book for additional information. Also note that good vitamin D status is important for the mother's health as well as for the infant. Mary B Johnson Minnesota WIC Program