Objective To analyze the prevalence of developmental dysplasia of the hip (DDH) in Tianjin,and to establish early screening of DDH in China.Methods System of health care for maternity and children in Tianjin were used to perform early ultrasound-screening program for DDH during the first 6weeks of life.The infants with abnormal conditions or suspected ultrasound results were transferred to Tianjin hospital.All the infants were clinically examined by experienced pediatric orthopaedic physician.Anteroposterior pelvic X-rays were taken for suspected infants to make a definite diagnosis.Results Hip ultrasound examinations were performed for 94 443 infants between December 26,2009 and December 25,2010.The 136 cases (165 hips) were suspected as DDH and 168 cases (200 hips) were diagnosed as DDH by ultrasound.All of them were transferred to Tianjin hospital.Among suspected patients,the positive signal of Ortolani or Barlow was found in 10 cases (11 hips).The DDH signal on the radiograph was positive in 73 cases (84 hips).Two hundred and fifty-one infants (295 hips) were finally diagnosed as DDH.There were 40 boys and 211 girls.Also,left hips and infants bom in autumn or winter were more often involved.The prevalence of DDH in Tianjin area was 2.66% (251/94 443).Conclusion Accurate early detection and diagnosis of DDH could be expected with the Tianjin pattern of preliminary screening,secondary screening and definite diagnosis.Careful clinical examination and X-ray are important for diagnosis.