Childbirth, also called labor and delivery, is the end of pregnancy. During childbirth, the baby (or babies in a multiple pregnancy) exits the uterus. Birth and delivery of the baby and the placenta is known as parturition. Labor is initiated by a decrease in progesterone, a hormone that maintains pregnancy, and an increase in the estrogen hormone estriol. Childbirth consists of three stages: dilation, delivery, and the placental stage.Dilation is the first stage of childbirth when the cervix softens and opens. Stage 1, dilation, starts with the beginning of contractions and dilates the cervix from 0 to 10 cm. It is the longest stage and is divided into three phases: early labor phase (beginning of contractions to a cervix dilated 3 cm), active labor phase (cervical dilation from 3 cm to 7 cm), and transition phase (cervical dilation from 7 cm to 10 cm). In stage 2, delivery, powerful uterine contractions push the baby out. In stage 3, the placental stage, the placenta is delivered.
The Stages of Childbirth
The second stage of birth involves delivery, in which the baby is delivered from the uterus. This can happen either vaginally or through a Caesarian section (C-section). In a vaginal birth, the mother pushes with contractions, moving the baby through the cervix and out of the body through the birth canal. In a C-section, the baby is delivered surgically through the abdomen. This procedure is used when the baby is in the incorrect position or there would be other complications to either the mother or child to have a vaginal birth.
The final stage of birth is the placental stage. In this stage, the placenta, which provided a connection between the fetus and the uterus, is delivered. This typically happens just a few minutes after birth of the baby. Oxytocin is responsible for continuing the contractions after birth of the baby in order to expel the placenta. Oxytocin also assists in clotting and reducing bleeding. It also has psychological effects, enhancing bonding between the mother and infant. After the placenta has been expelled, progesterone levels begin to rise, ceasing contractions.
In the weeks and months after childbirth, prolactin and oxytocin levels remain high, as both hormones assist with breastfeeding and lactation, the secretion of milk from the mammary tissue of the breast. Eventually, estrogen, progesterone, and ovarian hormones return to typical levels, resuming the woman's ovarian and uterine cycles. The female breast normally grows during pregnancy because of mammary glandular development and fat deposition. During this time, the areolae and nipples also enlarge. The mammary glands are responsible for milk production. For every 15 to 20 lobes of glandular tissue, a lactiferous duct (channel that connects the nipple to the lobules of the mammary gland) drains the milk and directs it toward individual openings on the nipple. A dilated portion of the lactiferous duct, called the lactiferous sinus, is positioned just below the areola and is where the droplets of milk accumulate in the nursing mother. When an infant begins to suckle at the nipple, the areola is compressed and the accumulated milk in the lactiferous sinus is released.
In the first two to three days after delivery, a special type of milk, called colostrum, is produced. It contains white blood cells and antibodies, particularly immunoglobulin A (IgA), in addition to a large percentage of proteins, minerals, and fat-soluble vitamins. This colostrum is very important in that it not only fulfills the infant's nutritional requirements, but helps protect the baby from infectious agents in the environment. Milk is produced in larger amounts on days two through four. By two weeks after birth, milk is considered to be mature.