Objective: To assess the prevalence and severity of postpartum injury to anal sphincter using trasperineal sonography .To identify maternal and obstetrical risk factor for this adverse outcome. Material and Methods: This is a prospective study of pregnant women in their third trimester , registered in the hospital during the period June 2006 to aug 2007 .TPUS was done in both antenatal & postnatal period & images were compared with relation to the effect of parity ,mode of delivery ,use of episiotomy ,duration of labor and weight of baby. Results: In the present study 40 antenatal patients were enrolled, 20 were primigravida & 20 multiparous.