In humans the fetus, placenta and fetal membranes play the major role in initiation and continuation of labor. Alteration of estrogen and progesterone ratio leads to prostaglandin synthesis. Prostaglandins play an important role in initiation of parturition. Primary effect of PGs at term is by increase in synthesis and myometrial sensitivity through formation of gap junctions. Uterus has no pacemaker that is demonstrable anatomically, physiologically or pharmacologically. Contractions start near one cornual region and the wave of contraction spread downward. Contraction of voluntary muscles of abdominal wall reinforcing uterine contractions to expel the fetus during second stage. Intra-abdominal pressure is raised thereby augmenting intrauterine pressure. Factors responsible for dilatation of cervix are uterine contraction and retraction. Longitudinal muscle fibers of upper segment are attached with circular muscle fibers of lower uterine segment and upper part of cervix in a bucket holding fashion. Cardinal movements of fetus takes place during pelvic division of labor. Fetal descent pattern of normal labor show hyperbolic curve where station of head is plotted as a function of duration of labor. Rhythmic uterine contractions occur causing placental separation, descent into lower uterine segment and finally expulsion. Marked retraction reduces the surface area at the placental site resulting in shearing of the placenta from the placental site. Vaginal examination is done to know the stage of labor. Effacement, dilatation, station, membranes, caput, moulding and also adequacy of pelvis is noted. Retraction of interlacing muscle fibers around the uterine vessels causes the clamping effect. Thrombosis and apposition of uterine wall also help in minimizing blood loss. Retraction of interlacing muscle fibers around the uterine vessels causes the clamping effect. Thrombosis and apposition of uterine wall also help in minimizing blood loss. Stage following delivery of placenta for a period of one hour to watch for any complications like postpartum hemorrhage, vulval hematoma and uterine inversion.