By Dana Dovey
The shape and density of women’s spines put them at greater risk for developing scoliosis and osteoporosis. This physical difference in spinal structure between the sexes is unique to humans, but it’s purpose has long puzzled scientists. A recent study, however, has provided evidence to suggest these differences are present at birth, and that they occur because a woman’s spine serves an integral role in helping women adapt to the physical challenges of pregnancy.
For the study, now published in the August issue of the Journal of Pediatrics, a team of researchers at Children’s Hospital Los Angeles used magnetic resonance imaging (MRI) to study the dimensions of 70 full-term newborns (35 boys and 35 girls). According to the press release, newborns’ body lengths, heads, waist circumferences, and weight did not differ greatly between the sexes. However, the strength of the female newborns’ vertebrae, as measured by their vertebral cross-sectional dimensions, consistently measured about 10.6 percent less than that of the male newborns. This finding is important because not only does it mark the first time that differences in spinal structure were found in children so young, but it also hints at the trait’s greater purpose. 
“Although we’ve known that girls had smaller vertebrae than boys, we did not know how early this difference first occurred,” senior author Vicente Gilsanz explained in a statement. “Our study indicates that the distinction between sexes is already present at birth and provides new evidence that this difference begins during prenatal development of the axial skeleton.”