Objectives. To describe the clinical characteristics and outcomes of a large group of women with symptom‐giving pelvic girdle relaxation of pregnancy and postnatal pelvic joint syndrome. To determine if there is an increased incidence of developmental dysplasia of the hip in the children of women with such pelvic problems.Methods. A postal survey of 1,609 Norwegian women registered as having pregnancy‐initiated pelvic joint pain. The response rate was 79% and from the answers 1,115 women were defined as having had symptom‐giving pelvic joint syndrome of pregnancy and/or postnatal pelvic joint syndrome.Results. Pelvic pains began in the first pregnancy in 74% of the respondents usually beginning in the first trimester. Pelvic pain worsened with subsequent pregnancies and persisted for a mean of 6.25 years, often causing major incapacity and lifestyle changes. Rest and physical supports brought temporary relief only. Sacroiliac joints and the symphysis pubis were the commonest sites of pain but peripheral joints were also often affected. There was a strong family history of both pelvic joint syndrome and developmental dysplasia of the hip. The incidence of hip dysplasia in the children of women surveyed was 45/1,000 which is 5 times the Norwegian incidence.Conclusion. Pelvic joint syndrome nearly always follows pelvic girdle relaxation of pregnancy and may have prolonged debilitating effects which do not respond long term to current therapies. The incidence of developmental dysplasia of the hip in the children of these women was high. A genetic susceptibility to joint dysfunction in both mother and fetus, possibly due to an aberration of relaxin physiology, is surmized. Identification of possible relaxin receptor changes in affected joints is a hypothesis worthy of testing with a view to the design of selective relaxin receptor modulators in pregnancy.