Some aches and pains are normal during pregnancy, and probably the most common complaint you'd hear from pregnant women is backache. As pregnancy progresses, the weight of the baby pulls her center of gravity to the front and she tries to compensate by leaning backwards. That's why you see so many heavily pregnant women with an awkward posture, with an impossibly deep curve at the base of their spine. But did you know that women's spine have evolved and are different from men's precisely for this reason - to prevent injury due to an exaggerated spinal curve?

Exaggerating the curve in the lower back can place more stress on the spine: vertebrae are more likely to slip against each other, leading to back pain or fractures. Whitcome and her colleagues found that a woman's spine has several features that help to prevent that damage. In women, the curve in the lower back spans three vertebrae; in men, it encompasses just two. The added vertebra helps distribute the strain over a wider area.

In addition, specialized joints located behind the spinal cord, called zygapophyseal joints, are 14% larger relative to vertebrae size in women than in men, suggesting that the joints are well adapted to resist the higher force. The joints are also oriented at a slightly different angle in women, allowing them to better brace the vertebrae against slipping.

Seems that Arnold Schwarzenegger's film Junior would be impossible in real life after all. Isn't it amazing how nature made it sure that women's bodies are made to withstand having a baby?

Photo Credit: ballison