The onset of labor is usually marked by the patient’s becoming conscious of the uterine contractions through dragging pains which may be felt first in the back and then in the lower part of the abdomen and the thighs. At first the pains are feeble and infrequent, but they gradually grow more severe and more frequent. Intestinal colic is sometimes mistaken for labor pains, but when the paroxysms are rhythmical and the uterus is felt, through the abdominal wall, to grow hard as the pain increases and soft as it subsides, there can be no doubt but that the patient is in labor. The first signs of labor may be a gush of amniotic fluid, caused by the rupture of the membranes, or of blood, but these are not typical. For purposes of convenience, labor is usually described as consisting of three periods or stages. The first stage begins with the onset of labor and lasts until the cervix is completely dilated; the second stage begins with the complete dilatation of the cervix and lasts until the child is born; the third stage begins with the birth of the child and lasts until the placenta is expelled. The entire duration of labor may vary from a few moments, comprising a few pains, to several days of severe and exhausting pain, but the average length of the first labor is 18 hours and of subsequent labors about 12 hours, divided respectively into the three periods as follows: _1st stage._ _2nd stage._ _3rd stage._ _Total._ Primipara 16 hours 1¾ hours 15 minutes 18 hours. Multipara 11 hours 45 minutes 15 minutes 12 hours. The longer labor in primiparous women is due to the greater tone, and thus the greater resistance offered by the muscles of the cervix and perineum. Elderly primiparæ are likely to have longer labors than young primiparæ. =First Stage.= This is frequently called the stage of dilatation. During this period the contractions of the uterine muscles make pressure upon the amniotic sac of fluid, forcing it gradually down and into the cervix as a water wedge, widening the internal os first, then the external os, until the entire canal is fully dilated (thinned out); shortened to about one-half inch in length and finally obliterated so that it is uninterruptedly continuous with the lower uterine segment. (Figs. 63, 64, 65, 66.) The first stage pains begin by being mild and occurring at intervals of from 15 to 30 minutes, but they gradually increase in frequency and intensity until at the end of 14 to 16 hours they are very severe and recur every three or four minutes, each pain lasting about one minute. The pains begin in the back, pass slowly forward to the abdomen and down into the thighs.