Background: Pregnancy-related pelvic girdle pain (PGP) can appear during pregnancy, directly after labour or can be delayed to 3 weeks postpartum. Pain is experienced between the posterior iliac crest and the gluteal fold, particularly in the vicinity of the Sacroiliac joints (SIJ). The pain may radiate in the posterior thigh and can also occur in conjunction with/or separately in the symphysis. The endurance capacity for standing, walking, and sitting is diminished. The diagnosis of PGP can be reached after exclusion of lumbar causes. The pain or functional disturbances in relation to PGP must be reproducible by specific clinical tests. Lack of accurate and early diagnosis of the PGP reasons postpartum may contribute to development of chronic condition, lowering quality of life years after delivery.

Objectives: The aim of the project is to evaluate the underlying cause of the severe pelvic girdle pain postpartum (whether it is real PGP or diastasis pubic symphysis) and to assess the differences between females with severe postpartum PGP, mild and moderate PGP and with no PGP in terms of: presence of diastasis pubic symphysis, presence of diastasis recti and linea alba dysfunction, factors associated with labour and maladaptive mental processing (catastrophizing).

Materials and methods: Because of low incidence of researched conditions, a case control study will be the study design of choice. The subjects with PGP will be matched with those with no PGP. Subjects' assessment will consist of palpation and ultrasonography evaluation of diastasis recti(inter-recti distance), ultrasonography assesment of pubic symphysis (inter-pubic width) and mental processing (catastrophizing assessed with Pain Catastrophizing Scale) analysis. Factors connected with labour (time from epidural anaesthesia injection to full dilatation and delivery) will be also investigated.

Expected results: To the investigators' knowledge, postpartum pelvic girdle pain has not been extensively studied so far. The study will bring information about the possible underlying cause of postpartum PGP: whether it is PGP or diastasis pubic symphysis.

Inclusion Criteria:

• Natural labour or vacuum extractor or forceps
• for the study group - pain due to PGP confirmed with dedicated functional tests
• for control group with no pain - no pain due to PGP
• agreement to participate

Exclusion Criteria:

• diseases that can mimic PGP f.ex. Scheuermann disease, rheumatoid arthritis, Ehler's-Danlos Syndrome, hip dysplasia
• major peri-partum events like internal haemorrhage, pelvic fracture

Women in early postpartum period (during hospital stay)