With this study, we wanted to determine the incidence of symptom-giving pelvic girdle relaxation during pregnancy and the prevalence post partum, identify predisposing factors, and determine the frequency of sick leave. A total of 1600 pregnant women entered the study. The incidence during pregnancy was 14%, the prevalence two, six, and twelve months post partum was 5%, 4%, and 2%, respectively. Multivariate analysis indicated that the most important predisposing factor was pelvic pain in a previous pregnancy. Other factors were uncomfortable working conditions, lack of exercise, and previous low back and low abdominal pain. At least 37% of the women with symptom-giving pelvic girdle relaxation were on sick leave during pregnancy, on average for twelve weeks. Symptom-giving pelvic girdle relaxation is a considerable problem both in pregnancy and post partum. The occupational risk can possibly be prevented. The syndrome has a great social impact because of the high frequency of sick live.