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.
The patient is entirely comfortable, as a rule, between pains and until they become very frequent will usually feel able, in fact prefer, to be up and about, but if she is on her feet when a contraction begins she will usually seek relief by assuming a characteristic leaning position (Fig. [67]) or by sitting down, until the pain subsides. As dilatation advances, the patient has an increasing, sometimes persistent, desire to empty the bowels and bladder because of encroachment upon these two organs by the descending head. She may vomit, also, when the cervix becomes nearly or quite dilated.
Fig. 63.
Fig. 64.