Dystocia and Augmentation of Labor

I. Normal labor

A. First stage of labor

1. The first stage of labor consists of the period from the onset of labor until complete cervical dilation (10 cm). This stage is divided into the latent phase and the active phase.

2. Latent phase a. During the latent phase, uterine contractions are infrequent and irregular and result in only modest discomfort. They result in gradual effacement and dilation of the cervix.

b. A prolonged latent phase is one that exceeds 20 hours in the nullipara or one that exceeds 14 hours in the multipara.

3. Active phase a. The active phase of labor occurs when the cervix reaches 3-4 cm of dilatation.

b. The active phase of labor is characterized by an increased rate of cervical dilation and by descent of the presenting fetal part.

B. Second stage of labor

1. The second stage of labor consists of the period from complete cervical dilation (10 cm) until delivery of the infant. This stage is usually brief, averaging 20 minutes for parous women and 50 minutes for nulliparous women.

2. The duration of the second stage of labor is unrelated to perinatal outcome in the absence of a nonreassuring fetal heart rate pattern as long as progress occurs.

II. Abnormal labor

A. Dystocia is defined as difficult labor or childbirth resulting from abnormalities of the cervix and uterus, the fetus, the maternal pelvis, or a combination of these factors.

B. Cephalopelvic disproportion is a disparity between the size of the maternal pelvis and the fetal head that precludes vaginal delivery. This condition can rarely be diagnosed in advance.

C. Slower-than-normal (protraction disorders) or complete cessation of progress (arrest disorder) are disorders that can be diagnosed only after the parturient has entered the active phase of labor.

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