Labor is the sequence of events including uterine contractions, dilatation and effacement of the cervix (the mouth of the uterus), and the attempt to push the fetus down and out of the vagina. It is common in text books to describe the 3 stages of labor: first stage: from the onset of labor (characterized by regular uterine contractions that in time becomes more frequent, more intense and is of longer duration) to full dilatation of the cervix (10 cm). second stage: from the time when the cervix is fully dilated to the birth of the infant. third stage: from the birth of the infant to the time when the placenta is delivered.