Inclusion Criteria:  Women between 18 and 49 years old; Primiparous or multiparous;  Since the first moments up to 8 weeks after vaginal delivery (including spontaneous and assisted):  of singleton, live foetus, in any presentation, in gestational week 34 or more.  For group A:  no clinical signs of any degree perineal tear no clinical signs or symptoms of any damage involving anal sphincters; presence of not more than 1 of following OASIS risk factors related to the last delivery: prolonged second phase of delivery, foetal shoulder dystocia, birth weight of the neonate >4kg, induction of delivery using oxytocin, or head circumference of the neonate ≥34 cm  For groups B and C:  clinically confirmed 1 or 2-degree perineal tear (including episiotomy and uncontrolled crotch rupture) occurred at the last delivery (for group B); clinically identified 3 or 4-degree perineal tear (damage involving anal sphincters) occurred at the last delivery (regardless of primary repair) (for group C); Signed informed consent form (no proxy or witnessed consent allowed).  Exclusion Criteria:  Any acute, uncontrolled disease (except for haemorrhoidal disease) Chronic diseases not treated or not stable on treatment; Symptoms of faecal incontinence due to a disease other than diagnosed or suspected OASIS; Previous surgery for OASIS (primary or secondary), faecal incontinence or anal prolapse, except for a primary repair of anal sphincter damage performed after the last delivery (allowed); Any surgery in perineal or rectal area, including surgery for OASIS, planned for the study period Presence of inflammatory bowel diseases during exacerbation phase; Any treatment during last 12 months for severe, progressive, uncontrolled cardiological, pulmonary, nephrology, contagious or psychiatric illness that could increase subject's risk due to participation in the study, Disease other than OASIS so far undiagnosed and reported during the visit V1 or within 7 days prior to it; Present or suspected malignancy or previous oncological treatment in the last 5 years; Implanted cardiac stimulator or cardioverter-defibrillator; Clinically significant cardiac arrhythmias observed in ECG examination or reported in history for the last 12 months; Fever (>37°C) at enrolment; History of major surgery in perineal or rectal area (other than for OASIS) or severe trauma of perineum or rectum. Use, or need for use, of an anal suppository or other anally administered drug, or cosmetic for the perianal area, within 12 hours prior to impedance spectroscopy examination (visit V2). Positive pregnancy test (only for subjects recruited ≥4 weeks after delivery with no lactation at V1 visit; however, subjects with a positive pregnancy test may be enrolled as long as gynaecologic ultrasound performed at V1 visit shows no signs of a new pregnancy, no sings suggestive of placental tissue remaining in utero, or other abnormality of the uterus).