A new study suggests that girls are born with smaller and weaker backbones than boys. Researchers took magnetic imaging studies of 70 healthy newborns, 35 of which were girls, and measured fat, muscles, and bone. Boys had slightly less fat and slightly more muscle than the girls, but there wasn’t a big enough statistical difference. There also was not a statistical difference in weight, body length, head circumference, waist circumference, or spinal length.
However, the girls’ vertebrae were 10.6 percent smaller, on average, than the boys. There was no other difference in the size of other bones between the boys and girls.
As adults, women are four times as likely to suffer vertebral fractures than men. However, this depends on the size of the vertebrae and less on the density of the bone.
Radiologist at Children’s Hospital Los Angeles, Dr. Vicente Gilsanz says that a girl’s bendable and slender spine may be a mixed blessing. He says it allows for upright walking during pregnancy when the weight of the baby stretches and bends the spine. However, this also can increase the risk for vertebral fractures later in life.