The post partum pubic symphysis diastasis is an uncommon disease. It is resposible of acute pelvic pain. It increases when manual pressure is applied to the pelvis in a latero-lateral and antero-posterior direction. The diagnostic test for this condition is an anteroposterior X-ray of the pelvis. Here we present a case following spontaneous vaginal delivery. The conservative treatment is able to obtain good results. If this disease is underestimated the patient can develop chronic pain.