What is Childbirth

Childbirth - The passage of the FETUS from the UTERUS to independent life outside the woman’s body as PREGNANCY culminates. The physiologic processes that establish this passage are labor and delivery (vaginal birth); childbirth may also occur as a surgical procedure (CESAREAN SECTION). Labor refers to the progressively intense contractions of the uterus that dilate and efface (stretch and thin) the CERVIX, then push the fetus into and through the VAGINA (birth canal).

Though labor and delivery occur in predictable and sequential stages, their timing varies widely. Early labor may last a few to 36 hours. Active labor generally lasts 2 to 8 hours. Delivery, the passage of the baby through the birth canal, may take 15 minutes to 2 hours. A woman’s first delivery typically takes longer than subsequent deliveries. Though childbirth is a natural process, in the United States most childbirth takes place in hospitals or birthing centers with medical professionals (doctors, nurses, midwives) providing care and assistance.

Childbirth Stage 1: Labor

Labor is the work of the uterus and abdominal muscles to ready the woman’s body for birth and ultimately push the infant out. For more than 40 weeks the body’s focus has been on maintaining the pregnancy within it. As the time for birth approaches, hormonal signals initiate the sequence of events that will make delivery possible. Researchers do not know what starts the hormonal cascade that ultimately results in childbirth, though these changes begin some time before actual labor starts.

Though the most intense experience of labor is in the hours that lead to delivery, the preparations actually begin several weeks before birth. One of the earliest signs of impending birth is the dropping of the presenting part of the fetus, usually the head, into the start of the cervix. Called engagement or lightening, this movement indicates the cervix is beginning to efface. It also signals changes that are occurring within the fetus to prepare it for life outside the womb, notably expansion of the LUNGS.

As the cervix continues to efface and begins to dilate the plug of mucus that formed in the cervical canal comes loose and slides out, which the woman may notice as a brownish discharge (sometimes called bloody show). This may occur a week or longer before birth. The characteristic experience of labor begins with sensations of tightening and relaxing in the lower abdomen, somewhat similar in experience to menstrual cramps. Many women feel these sensations in the lower back as well. The woman may feel restless and want to walk around; walking helps strengthen and coordinate contractions as they progress. Labor becomes more intense and focused when the membranes rupture, often called water breaking.

There are many ways women cope with the discomfort of labor, which intensifies as the labor progresses. Methods such as relaxation BREATHING, massage, acupuncture, and visualization often help a woman feel calm and centered. Some women become intensely active in the early stages of labor, cleaning house and otherwise “nesting.” Doctors believe this behavior harkens to primal instincts of preparedness. In early labor contractions may be 10 to 15 minutes apart and last about 30 seconds and may become less intense with certain positions or activities. As early labor progresses to active labor, contractions are about 5 minutes apart and last for 45 to 60 seconds.

In active labor contractions continue to increase in frequency and intensity, and discomfort progresses to PAIN. Many women feel the need for pain relief during active labor. Common methods include narcotic ANALGESIC MEDICATIONS and regional ANESTHESIA such as epidural block. Active labor dilates the cervix to 7 or 8 centimeters.

The final stage of labor is transition, during which contractions come in waves often without more than seconds between them. Transition consumes the woman’s attention and focus; she often is not aware of activity taking place around her. Many women feel the urge to push, though should not do so because the cervix is not yet ready. Transition is usually complete within three hours. The cervix finishes dilating to a wide-open 10 centimeters, and birth is imminent.

Childbirth Stage 2: Delivery of the Baby

Delivery requires much conscious effort from the woman to push with contractions. The birthing team coaches and guides the process. The urge to push may be overwhelming; going with it is usually the most efficient approach unless the doctor or midwife advises to wait. Sometimes the baby’s position in the birth canal becomes awkward such that waiting a few moments allows a turn or movement that then responds better to pushing. An epidural for pain relief tends to extend delivery somewhat because the woman does not as strongly feel the urge to push.

The head emerges first, with the shoulders and then the rest of the body following. The doctor or midwife suctions any mucus and BLOOD from the baby’s NOSE and MOUTH. The baby begins breathing as soon as his or her body clears the birth canal and the chest can expand. When all is well, the doctor or midwife places the baby on the mother’s chest for her to hold and clamps the UMBILICAL CORD in two places. The partner, the mother, an older sibling present for the birth, or the birthing attendant may cut between the clamps to sever the cord.

Childbirth Stage 3: Delivery of the Placenta

After a brief pause contractions resume to separate the PLACENTA from the endometrium and push it from the body. It takes about 10 minutes to deliver the placenta, which sometimes requires the woman to bear down to help push it out. The uterus then continues mild contractions, which are important to restore its firmness and to stop bleeding. A member of the birthing team may massage the mother’s lower abdomen to further stimulate these contractions. BREASTFEEDING the infant at this time is also helpful because the sucking at the BREAST releases OXYTOCIN, a HORMONE that continues the uterine contractions as well as releases colostrum (premilk) for the infant.

For further discussion of childbirth, please see the overview section “The Reproductive System.”


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The Reproductive System

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