Sexual Dimorphism in Newborn Vertebrae and Its Potential Implications

Objective To examine whether the sex-related differences in vertebral cross-sectional area (CSA) found in children and at the timing of peak bone mass–a major determinant of osteoporosis and future fracture risk–are also present at birth. Study design Vertebral CSA, vertebral height, and intervertebral disc height were measured using magnetic resonance imaging in 70 healthy full-term newborns (35 males and 35 females). The length and CSA of the humerus, musculature, and adiposity were measured as well. Results Weight, body length, and head and waist circumferences did not differ significantly between males and females ( P ≥ .06 for all). Compared with newborn boys, girls had significantly smaller mean vertebral cross-sectional dimensions (1.47 ± 0.11 vs 1.31 ± 0.12; P