Childbirth
Second stage: fetal expulsion

The expulsion stage begins when the cervix is fully dilated, and ends when the baby is born. As pressure on the cervix increases, a sensation of pelvic pressure is experienced, and, with it, an urge to begin pushing. At the beginning of the normal second stage, the head is fully engaged in the pelvis; the widest diameter of the head has passed below the level of the pelvic inlet. The fetal head then continues descent into the pelvis, below the pubic arch and out through the vaginal opening. This is assisted by the additional maternal efforts of pushing, or bearing down, similar to defecation. The appearance of the fetal head at the vaginal opening is termed crowning. At this point, the mother will feel an intense burning or stinging sensation.

When the amniotic sac has not ruptured during labour or pushing, the infant can be born with the membranes intact. This is referred to as "delivery en caul ".

Complete expulsion of the baby signals the successful completion of the second stage of labour. Some babies, especially preterm infants, are born covered with a waxy or cheese-like white substance called vernix. It is thought to have some protective roles during fetal development and for a few hours after birth.

The second stage varies from one woman to another. In first labours, birth is usually completed within three hours whereas in subsequentlabours, birth is usually completed within two hours. Second-stage labours longer than three hours are associated with declining rates of spontaneous vaginal delivery and increasing rates of infection, perineal tears, and obstetric haemorrhage, as well as the need for intensive care of the neonate.
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