Causes

At birth, the hip joint is made of soft cartilage that gradually hardens into bone. The ball and socket need to fit together well because they act as molds for each other. If the ball isn't seated firmly into the socket, the socket will not fully form around the ball and will become too shallow.

During the final month before birth, the space within the womb can become so crowded that the ball of the hip joint moves out of its proper position, which results in a shallower socket. Factors that may reduce the amount of space in the womb include:

• First pregnancy
• Large baby
• Breech presentation