Endogenous synthesis accounts for the majority of vitamin D in adults (8). Above latitude 42 in the northern hemisphere, synthesis is limited to late spring through mid-autumn, because of the low intensity of UVB radiation, during the rest of the year. The majority of Canadians reside north of the 42nd parallel, placing them at risk for hypovitaminosis D year round because of the use of sunscreen and environmental factors, such as clothing and pollution, which reduce exposure to UVB sunlight (14). This means that endogenous synthesis in pregnant women and subsequent maternal-fetal transfer may be compromised. Fortified foods such as milk, margarine and vitamin supplements remain the major source of vitamin D for many Canadian adults.