Stages of labor
Labor is a continuous process. For clinical purposes, however, it is divided into three stages:
1 The first stage refers to the interval between the onset of labor and full cervical dilation. It is further divided into the latent phase (the period between the onset of labor and a point at which a change in the slope of the rate of cervical dilation is noted) and the active phase (which is associated with a greater rate of cervical dilation and usually beings at around 3–4 cm dilation). The partogram (Friedman curve) is a graphic representation of the normal labor curve against which a patient’s progress is plotted (Figure 61.1). Normal latent phase is <20 hours in nullipara and <14 hours in multipara. In active phase, the cervix should dilate a minimum of >1.2 cm/h in nullipara (>1.5 cm/h in multipara) (Figure 61.2). A delay in cervical dilation in the active phase of ≥2 hours over that expected suggests labor dystocia and requires further evaluation.
2 The second stage commences when the cervix achieves full dilation (10 cm) – not when the mother starts to push – and ends with delivery of the fetus. Prolonged second stage refers to >3 hours with or >2 hours without regional analgesia in a nullipara and >2 hours with or >1 hour without regional analgesia in a multipara.
3 The third stage refers to delivery of the placenta and fetal membranes and usually lasts <10 min. In the absence of excessive bleeding, up to 30 min may be allowed before intervention (see Chapter 68).
Cardinal movements in normal labor (Figure 61.3)
The cardinal movements refer to the changes in position of fetal head required for the fetus to successfully negotiate the birth canal and include the following:
