Objectives: Vitamin D plays a critically important role in the development, growth, and mineralization of the skeleton during its formative years, and performs an equally essential role in maintaining a healthy mineralized skeleton for adults of all ages. We evaluated the vitamin D status and risk factors for vitamin D deficiency in healthy breast-fed newborns and their nursing mothers.Methods: Serum 25-hydroxyvitamin D (25OHD), calcium, phosphorus, and alkaline phosphatase levels were measured in 54 newborns and their nursing mothers whose ages ranged from 18 to 38 y. The relation between serum 25OHD level and demographic factors was analyzed. Bone mineral density was measured in the mothers with a serum 25OHD level below 25 nmol/L to determine the extent of bone mineralization.Results: The mean serum 25OHD level in the 54 mothers was 29.11 +/- 10.47 nmol/L. Forty-six percent of the mothers had serum 25OHD levels below 25 nmol/L. The risk factors for low maternal serum 25OHD level were found in decreasing order of importance as follows: low socioeconomic class (odds ratio [OR] = 8.1, P = 0.000), being covered (OR = 4.3, P = 0.023), and low educational level (OR = 3.5, P = 0.033). The mean serum 25OHD level in the newborns was 18.62 +/- 8.00 nmol/L. Eighty percent of the newborns had serum 25OHD levels below 25 nmol/L. There was a significant correlation between the serum 25OHD levels of the newborns and their mothers (r = 0.63, P = 0.01). The most important risk factor for low serum 25OHD level in the newborn was a maternal 25OHD level below 25 nmol/L (OR = 15.2, P = 0.002), followed a covered mother (OR = 6.8, P = 0.011). Bone mineral densitometry showed osteopenia in 40% of the women with serum 25OHD levels below 25 nmol/L. All women were from a lower socioeconomic class and 80% were covered.Conclusions: Vitamin D deficiency is still a common and serious health problem of women of reproductive age and their babies in developing countries at the outset of a new millennium.