The duration of this stage is variable. It is much longer in primiparas than multiparas. It averages sixteen hours in the former, and eight hours in the latter. Vomiting during this stage is quite common, but the pulse and temperature remain normal. The first stage of labor is usually under the entire control of the nurse. It is her responsibility.
With complete dilatation of the os, the second stage, or stage of expulsion, begins, whether the membranes rupture or not. The presenting part, usually the head, passes from the cervix into the vagina. The vagina in turn gradually dilates from above downward until uterus, cervix and vagina form a single, wide channel of the same diameter. The child is driven forward by the uterine contractions, strongly reinforced by the abdominal muscles, which the patient uses vigorously. The onset of each pain is accompanied by a deep inspiration, followed by straining or bearing down with the abdominal muscles as in a highly exaggerated bowel movement. The patient holds her breath, braces her feet, fastens her hands on bed or attendant, and uses all the trunk muscles in the effort. The face becomes congested, the pulse quickened, she perspires some, and groans deeply during the contraction. The pain is extreme and is due partly to the stretching of the vagina and vulva and partly to the distention of deeper sensitive structures.
When the head reaches the pelvic floor, the first change observed in the external genitals is the stretching (bulging) of the perineal body. Next, the anus becomes turgid, dilates slightly, the anterior wall becomes visible, and the hairy scalp of the child appears at the vulva. The actual expulsion of the head in a primipara is accomplished by a series of prolonged and severe contractions, accompanied by violent straining.
Fig. 40.—The cervix is effaced, and the os dilated. The second stage begins. (Eden.)
Fig. 41.—Child in second stage of labor with bag of waters unruptured and presenting at the vulva. (Braune, from Barbour.)
A short pause ensues, followed in two or three minutes by a return of the pains, which expel first the shoulders and then the trunk. As the body escapes it is followed by a rush of blood-stained liquor amnii. This is the fluid that has been pent up in the uterus by the obstructing body of the child. The second stage lasts about two hours in a primipara and from fifteen minutes to one hour in a multipara.
The third stage is the delivery of the after-birth. The after-birth sometimes called the secundines, consists of placenta, umbilical cord, and membranes.
