Developmental hip dysplasia is the most common hip disorder. The incidence of this disease is affected by many factors, such as geography, living habits and ethnicity, and its incidence is highly correlated. The incidence is also higher in Japan and American Indian tribes. Our data is roughly: the incidence rate of surviving children is 1%. The left side is more than the right side about 10:1, and the right side is more important for bilateral dislocation. It is mostly seen in females, and the ratio of males to females is about 1:5-6. The incidence is low in ethnic groups that are used to carrying babies on their backs; the incidence is significantly higher in ethnic groups that prefer to use tying methods. The incidence is significantly higher for babies born in winter. The incidence of breech birth is higher, about 23% in foreign countries, 26% in Shanghai, 28.5% in Shenyang, and only 5% in normal births; breech birth is 10 times higher than cephalic birth; caesarean section is higher than vaginal birth, accounting for 30% in Shanghai statistics, and there is a significant difference, and it is also found that the incidence of babies with heavy body weight in caesarean section is high. Therefore, screening for developmental hip dysplasia needs to be done as early as possible for the high-risk group. If the baby is less than six months old, it can be screened by ultrasound, while babies older than six months need to be X-rayed to get a diagnosis. High-risk groups include breech, girls, firstborns, twins, family history, combined clubfoot or clubfoot, etc.