The frequency of rs1800012 polymorphism of alpha1-chains of type 1 collagen gene (COL1A1) was studied by real-time PCR in 422 Moscow women and children, including pregnant women (n=96), lactating (n=29) and non-pregnant women (n=28) and preschool children (2-6 years, n=76) and school children (7-16 years, n=193) with different levels of bone strength (BS) as determined by ultrasound densitometry. It was found that the decrease in the value of the BS (Z-score