In humans, the process of delivering a child from the uterus, usually by passage through the birth canal at the end of pregnancy, normally after a gestation period of about 267 days; also called parturition, or labor.
Childbearing is often viewed as the transition to adult female sexuality. Birth labor is divided into several stages. During the latent phase (Stage 0), 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 three or four centimeters. The mucus plug may be passed at this stage. The first stage of labor begins with uterine contractions accompanied by mild pain at intervals of about 10 to 20 minutes and sensations of discomfort in the small of the back which eventually become stronger and spread to the entire abdominal area. The cervix, or neck of the uterus, dilates rapidly from three or four centimeters until its opening is large enough to allow the passage of the child (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. The physician aids in the delivery by guiding the infant's head and shoulders out of the birth canal. About 2 to 3 percent of babies are born feet first (breech babies). Obstetrical forceps may be applied during the second stage of labor to speed delivery in order to ease either maternal exhaustion or infant distress. Other medical techniques utilized include the episiotomy, a surgical incision along the back of the vagina to enlarge the opening. (This procedure is now performed less frequently than it was in the past.)
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. During the third stage of labor, which occurs within the first hour after the child is born, placental material, or afterbirth, is expelled through the birth canal by strong uterine contractions called after-birth pains. These contractions also help the uterus to return to its normal size. The doctor examines the placenta and amniotic sac to confirm that all tissue has been expelled from the uterus, as serious complications may result if fragments remain inside, especially hemorrhaging. If parts of the placenta or sac are missing, the doctor removes them by hand. Finally, the episiotomy (if one has been performed) is sutured with absorbable stitches. The total duration of labor averages about 13 hours for first deliveries and about eight hours for subsequent deliveries, although there are large individual variances from these figures.
The pain of the birth process can be relieved by drugs, but many of these drugs also have the effect of slowing uterine contractions or depressing the respiratory system of the child. Drugs are either not used—or used with special care—in the case of twins or premature infants. Moderate doses of narcotic analgesics may be given to the mother, which are metabolized quickly and nearly absent by the time of delivery. Local anesthetics similar to Novocaine may be administered to provide pain relief in the cervical and vaginal areas, offering more localized relief with fewer side effects than narcotics. Methods of childbirth have been developed in which the use of drugs is kept to a minimum.
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 husband. 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, gave way to the establishment of birthing centers (in or affiliated with hospitals) staffed by nurse-midwives and obstetricians in an attempt to duplicate the family-centered, 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. In Birth Without Violence, the physician Frederick Leboyer described modern hospital birth as "torture of the innocent" and proposed measures to make the transition to life outside the womb a more gentle one for the newborn. 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.
Occasionally, complicating factors that can affect the mother, the child, or both are encountered in the birth process. These factors include, for example, poor health, anatomical abnormalities, prematurity, and unusual orientation of the child in the uterus, such as breech presentation, in which the child moves through the birth canal head last, and (rarely) transverse presentation, in which the child is positioned sideways. In some women, the pelvic space is too small for spontaneous birth of a baby, and the delivery of the child is accomplished through a surgical opening made in the mother's abdominal wall and uterus, in a procedure called a cesarean section. For a healthy mother and child, the risks of childbirth are extremely low. Premature labor, which occurs in about one pregnancy out of 20, is the primary danger to mother and child during the last trimester of pregnancy and the major cause of newborn death. About 40 to 50 percent of mothers—especially first-time mothers—experience mild post-partum depression, thought to be caused by a combination of biochemical factors and adjustment to the pressures and demands of parenthood. A smaller percentage— between 5 and 10 percent—become severely depressed. Postpartum depression usually lasts up to 90 days.
Abnormalities present at the time of birth, known as birth defects or congenital defects, occur in one of every 14 babies born in the United States. More than 3,000 birth defects have been identified, ranging from minor dark sports or a birthmarks to serious disfigurements or limited lifespans. Congenital heart defects occur to one of every 125 to 150 infants born in the U.S., making heart defects among the most common birth defects and the leading cause of birth defect-related deaths. Down syndrome is the most frequently occurring chromosomal abnormality, occurring to one of every 800 to 1,000 infants born in the United States. Annually, care of children with birth defects in the U.S. costs billions of dollars.
Birth defects have two causes: heredity and environment. Environment includes maternal illness, such as German measles. Other environmental factors include: alcohol and drugs, consumed during the pregnancy, and exposure to certain medicines or chemicals. Heavy alcohol consumption during pregnancy can trigger fetal alcohol syndrome in newborns, characterized by underweight, small eyes, a short upturned nose with a broad bridge, and often a degree of mental retardation. Thalidomide, prescribed in the 1950s as a mild sedative, led to the birth of 7,000 severely deformed babies, suffering from a condition called phocomelia, characterized by extremely short limbs that were often without fingers or toes.
For some diseases, like spina bifida, the causes are unknown but believed to be a combination of heredity and environment. Spina bifida, a neural tube defect, is the most frequently occurring permanently disabling birth defect in the United States, affecting one out of every 1,000 newborns. In spina bifida, the spine fails to close properly during the first month of pregnancy. In worst cases, the spinal cord protrudes through the back. A large percentage of children born with spina bifida have hydrocephalus, an accumulation of fluid in the brain which requires a surgical procedures called "shunting" to relieve the fluid build up and redirect it into the abdominal area. Sophisticated medical techniques allow most children with spina bifida to live well into adulthood. Based on research, the U.S. Public Health Service recommends that women of childbearing age in the U.S. consume 0.4 mg of folic acid daily to reduce the risk of having a pregnancy with spinal bifida or the other two neural two defects: anencephaly or encephalocele. Amniocentesis or ultrasound testing can diagnose spina bifida before birth.
Sickle-cell anemia, Tay-Sachs, color blindness, deafness, and extra digits on the hand or feet are hereditary birth defects passed on through generations by abnormal genes. Birth defects may not impact each generation, but the abnormal gene is passed on.
Hotchner, Tracy. Pregnancy and Childbirth: The Complete Guide for a New Life. 2nd ed. New York: Avon, 1990.
Martin, Margaret. The Illustrated Book of Pregnancy and Childbirth. New York: Facts on File, 1991.
Nathaniels, Peter. Life Before Birth and a Time to Be Born. Ithaca, NY: Promethean Press, 1992.
See also Fetal alcohol effect and syndrome