The commonest route of spread of puerperal sepsis is

The organisms responsible are typically those that normally colonize the cervix, vagina, and perineum and are usually of low virulence. The uterine cavity is sterile before rupture of membranes but later becomes contaminated. Other factors which help to create a suitable environment for these ascending organisms are tissue trauma, devitalization of tissues and the alkaline lochia (refer pgno:434 Sheila 2 nd edition)