Final answer:
Early decelerations in labor are caused by the baby's head being compressed against the cervix during the dilation stage. The expulsion stage involves the baby's head entering the birth canal, usually in the occiput anterior vertex orientation. Pitocin can be used if labor stalls to maintain contractions.
Step-by-step explanation:
Early decelerations in labor occur as a result of the baby's head being compressed against the cervix. This compression happens during the cervical dilation stage of labor, where uterine contractions become more intense and frequent, effectively pushing the baby's head against the cervix. This leads to the dilation of the cervical canal, necessary for the baby's head to fit through during the passage down the birth canal.
The expulsion stage of labor begins when the fetal head enters the birth canal and ends with the birth of the newborn. It can last up to 2 hours or longer, depending on the orientation of the fetus. The most common and easiest orientation for vaginal birth is the occiput anterior vertex, where the fetus faces the maternal spinal cord, and the occiput, the smallest part of the head, exits the birth canal first.
If labor stalls before the second stage is reached, Pitocin, a synthetic form of oxytocin, may be administered to restart and maintain contractions. However, during normal progression, the stretching of the myometrium and cervix by the full-term fetus in the vertex position stimulates more powerful and frequent uterine contractions, leading to successful labor and delivery.