peer reviewed ; We have evaluated the prevalence of the 25-hydroxy vitamin D (25VTD) deficiency in recently pregnant women and new mothers in the area of Liege, Belgium. The study took place in November 2006. Twenty four women who underwent a positive pregnancy test and 65 new mothers were enrolled. The level of 25VTD did not differ between the two groups. Only 12% of the pregnant women and 14% of the new mothers (>12 ng/ml) had an optimal level of 25VTD (>30 ng/ ml). We also observed a severe 25VTD deficiency in 21% of pregnant women and 32% of new mothers. Our results showed that more than 80% of pregnant women and new mothers in the area of Liege presented a deficiency in 25VTD. In Belgium, daily vitamin supplementation of pregnant women is common, but the level of vitamin D3 concentration range from 10 microg (400 UI) to zero microg. In our area, vitamin D production in the skin is not always important enough to achieve optimal levels. Our data show that vitamin D supplementation of pregnant women is not enough and that 25VTD deficiency is not diagnosed in this high-risk population. Children born from deficient mothers will present a higher risk of suffering from bone mineral diseases as well as other pathologies, as type 1 diabetes or neurological disorders. Of course, this insufficiency will also have an impact on mother's bone reserve, but these mothers will also be at higher risk for preeclampsia.