Because of more hormones in the body, girls start to have more fat in their breasts, abdomen, hips and thighs. At the age of ten years, the average girl has 6% more body fat than the average boy, but by the end of puberty the difference is nearly 50%. The fat makes sure that a baby growing inside a pregnant woman will have enough nutrients. Also, the bones in the pelvis move further apart to make room for a larger uterus and ovaries, and so there is space for a baby to grow in the uterus and to pass out of the body when it is born. The extra fat and wider hip bones that girls have give them a curvier shape.