Girls are seven times more likely to have this problem than boys. Twenty-five percent of CDH involves both hips. It is not possible to say exactly what has caused this. For instance, breech babies are more prone to have a dislocated hip than others. Premature babies seldom if ever have dislocated hips because they have more space in the uterus.
Hereditary factors play some part.
The hormone, estrogen, secreted during pregnancy, appears to cause a looseness in the joints, particularly of girl babies. This looseness may make it easier for the thigh bone to slip out of the socket and account for the fact that very many more girls are born with CDH than boys. All newborns are checked for this problem in the hospital and at follow-up visits with the doctor. Even with examination, however, a dislocated hip may escape notice during the first checks. But the displaced bone will tend to slip further up the hip so that it is usually discovered at an examination at some time in the first year of life, when the child begins to walk, or later.