The process of delivering a child from the uterus by passage through the birth canal or cesarean section at the end of pregnancy, which normally occurs after a gestation period of about 267 days; also called parturition, or labor.
Birth labor is divided into several stages. During the latent phase, which lasts from several hours to as long as three days, uterine contractions (either regular or irregular) are present, but the cervix has not dilated more than 3–4 centimeters. The mucus plug may be passed at this stage. Stage 1 labor begins with uterine contractions accompanied by mild pain at intervals of about 10–20 minutes and sensations of discomfort in the small of the back that eventually become stronger and spread to the entire abdominal area. The cervix, or neck of the uterus, dilates from three or four centimeters until its opening is large enough to allow the passage of the child's head (10 centimeters). By the end of the first stage (although sometimes much earlier), the sac containing the amniotic fluid which surrounds the child breaks. The first stage can take up to 12 hours with first-time mothers, although it may be very rapid in women who have had several children. It can last many hours in obstructed labor, where the baby is unusually large or badly angled.
The second stage of labor begins with the complete dilation and effacement (thinning) of the cervix and ends when the baby is born. At this stage, the contractions are increasingly frequent and intense, ultimately recurring at intervals of two to three minutes and lasting about a minute. The mother begins contracting her abdominal muscles voluntarily (“bearing down” ), and the baby is expelled, usually head first, by a combination of this voluntary contraction and the involuntary contractions of the uterine muscles.
Stage two labor is much shorter than stage one and can be exhausting and dangerous for the fetus if it lasts too long. If stage two labor lasts more than two hours without anesthesia or three hours with regional anesthesia in a woman birthing her first child or one hour without anesthesia or two hours with regional anesthesia in a woman who has birthed other children, additional medical intervention is considered appropriate based on concern for the health of the baby and mother.
Approximately 4% of babies are in what is called the breech position when labor begins. In a breech presentation, the baby's head is not the part pressing against the cervix. Instead the baby's bottom or legs are positioned to enter the birth canal first instead of the head. An obstetrician may attempt to turn the baby to a head down position using a technique called version. This is successful approximately half the time.
The risks of vaginal delivery with breech presentation are much higher than with a head-first presentation. The mother and attending practitioner will need to weigh the risks and make a decision on whether to deliver via a cesarean section or attempt a vaginal birth. The extent of the risk depends on the type of breech presentation, of which there are three. Frank breech (the baby's legs are folded up against its body) is the most common and the safest for vaginal delivery. The other types are complete breech (in which the baby's legs are crossed under and in front of the body) and footling breech (in which one leg or both legs are positioned to enter the birth canal first). These are considered unsafe situations in which to attempt vaginal delivery.
Other factors should also be considered before proceeding with a vaginal birth. An ultrasound examination may be done to be sure the baby does not have an unusually large head and that the head is tilted forward (flexed) rather than back (hyperextended). Fetal monitoring and close observation of the progress of labor are also important. A slowing of labor or any indication of difficulty in the body passing through the pelvis should be an indication that it is safer to consider a cesarean section.
If the labor is not progressing as it should or if the baby appears to be in distress, the doctor may opt for a forceps delivery. A forceps is a spoon-shaped device that resembles a set of salad tongs. It is placed around the baby's head so the doctor can pull the baby gently out of the vagina.
Before placing the forceps around the baby's head, pain medication or anesthesia may be given to the mother. The doctor may use a catheter to empty the mother's bladder, and may clean the perineal area with soapy water. Often an episiotomy is done before a forceps birth, although tears can still occur.
The obstetrician slides half of the forceps at a time into the vagina and around the side of the baby's head to gently grasp the head. When both sides are in place, the doctor pulls on the forceps to help the baby through the birth canal as the uterus contracts and the mother pushes.
A cesarean section is a procedure in which incisions are made through a woman's abdomen and uterus to deliver her baby. Cesarean sections are performed whenever abnormal conditions complicate labor and vaginal delivery, threatening the life or health of the mother or baby. The procedure may be used in cases where the mother has had a previous cesarean section and the area of the incision has been weakened. Dystocia, or difficult labor, is the another common reason for performing a cesarean section. Difficult labor is commonly caused by one of the three following conditions: abnormalities in the mother's birth canal; abnormalities in the position of the fetus; abnormalities in the labor, including weak or infrequent contractions.
Another major factor is fetal distress, a condition where the fetus is not getting enough oxygen. Fetal brain damage can result from oxygen deprivation. Fetal distress often is related to abnormalities in the position of the fetus or abnormalities in the birth canal, causing reduced blood flow through the placenta.
A cesarean section may also be advisable if the mother has an active sexually transmitted disease that can be transferred to the baby in a vaginal delivery, hypertension (high blood pressure), or diabetes.
When the baby is born, mucus and blood are removed from the nose and mouth by means of suctioning. The umbilical cord is clamped and cut, and the child is given to the mother to hold. The infant's physical condition is then assessed by the Apgar score, which evaluates the overall level of health based on heart rate, skin color, muscular activity and respiratory effort, and response to stimuli.
Stage three labor is the time between delivery of the baby and delivery of the placenta. Stage three labor usually lasts between 10 and 30 minutes. Contractions are less strong than in stage two labor. The placenta detaches from the uterus and easily slides through the birth canal. The entire placenta must be removed to prevent serious bleeding. If the placenta is not delivered in its entirety, medical intervention is necessary to remove it.
Childbirth education classes for the woman and her partner help a couple prepare for labor and delivery. Well before the birth is expected, couples should evaluate the options for the location and circumstances of the birth. Some couples choose to deliver their babies in their own homes or in birthing centers with a midwife as opposed to in a traditional hospital setting with nurses and physicians. Many medical professionals recommend against home births, as complications during delivery can arise quickly, and the woman and baby may not reach a hospital in time to prevent serious consequences including permanent disability and death. Many birthing centers have a relationship with a hospital where a woman can be transferred if complications arise.
The natural childbirth movement begun by Fernand Lamaze, which advocates birth without drugs or medical intervention, departed from the practices of the 1940s and 1950s, when the administration of drugs and medical procedures such as episiotomies were standard obstetrical procedure. Natural childbirth methods use nonmedical relaxation techniques for pain control and allow for more active participation in labor by the mother and a lay coach, usually the woman's partner. They typically include prenatal classes for the mother and coach. Women who use the Lamaze method are taught to perform three activities simultaneously during contractions: breathing in a special pattern, chanting a nonsense or meaningless phrase coordinated with the rhythm of her breathing, and staring intently at an object.
The home delivery movement, which became popular in the United States during the 1970s, has given way to the establishment of birthing centers (in or affiliated with hospitals) staffed by nurse-midwives and obstetricians in an attempt to duplicate the familycentered, drug-free experience of home birth but without the risks posed by the absence of medical professionals. The natural childbirth movement has also focused on easing the birth experience for the infant. These measures include dim lights and a quiet atmosphere in the delivery room, postponing cutting of the umbilical cord, and bathing the infant in lukewarm water. Psychologists Otto Rank and R.D. Laing have elaborated on the idea of birth trauma as a factor in adult mental and emotional problems, and Leonard Orr developed rebirthing in the 1970s as a holistic healing technique for eliminating negative beliefs that influence an adult's behavior and attitudes.
About half of all mothers, especially first-time mothers, experience mild postpartum depression (sometimes called the “baby blues” ), thought to be caused by a combination of biochemical and hormonal factors, exhaustion, and adjustment to the pressures and demands of parenthood. A smaller percentage— between 5 and 10%—become seriously depressed. Moderate to severe postpartum depression can and should be treated, both to benefit the mother and the child. In severe cases of postpartum depression, mothers have been known to attempt or complete suicide or to harm their child.
See also Fetal alcohol effect and syndrome.
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American College of Nurse-Midwives, 8403 Colesville Rd, Suite 1550, Silver Spring, MD, 20919, (240) 485-1800, Fax: (240) 485-1818, http://www.midwife.org .
American Congress of Obstetricians and Gynecologists, 409 12th Street SW, Washington, DC, 20024-9998, (202) 638-5577, (800) 673-8444, firstname.lastname@example.org, http:// www.acog.org .