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Premature birth Wikipedia

Premature birth (also known as preterm birth) is defined medically as birth occurring earlier than 37 completed weeks of gestation. Most pregnancy|pregnancies last about 40 weeks. Premature babies are sometimes called preemies. About 12 percent of babies in the United States - or 1 in 8 - are born prematurely each year. In 2003, more than 490,000 babies in the U.S. were born prematurely. The shorter the term of pregnancy is, the greater the risks of complications. Infants born prematurely have an increased risk of death in the first year of life. They are also at a greater risk for developing serious health problems such as: cerebral palsy, chronic lung disease, gastrointestinal problems, mental retardation, blindness|vision and deafness|hearing loss.

Although there are several known risk factors for prematurity (see below), nearly half of all premature births have no known cause. When conditions permit, doctors may attempt to stop premature labor, so that the pregnancy can have a chance to continue to full term, thereby increasing the baby's chances of health and survival. However, there is currently no reliable means to stop or prevent preterm labor in all cases.

After being born, a premature baby is cared for in a special section of the hospital known as the NICU (Neonatal Intensive Care Unit). The physicians who specialize in the care of very sick or premature babies are known as neonatologists. In the NICU, babies are kept in incubators, a bassinet enclosed in plastic with climate control equipment designed to keep babies warm and limit their exposure to germs. In some cases, an oxygen-enriched atmosphere may be used, although this is avoided where possible, as it can cause damaging side effects. Premature babies may be released from the hospital when they no longer need the constant hospital care the NICU provides.

There are many known factors related to premature births. However, the nature of the relationship between these factors and premature births are unclear.

• A woman's previous history of preterm birth, or pregnancies that ended in miscarriage.

The following symptoms may indicate a possible premature birth:

• 4 or more uterine contractions in one hour, before 37 weeks' gestation.

There are two tactics that can be used to deal with a potential premature birth: delay the arrival of birth as much as possible, or prepare the prospectively premature fetus for arrival. Both of these tactics may be used simultaneously.

Delaying the premature birth from occurring is typically the most favored option. This gives the fetus or fetuses as much time as possible to mature in the womb. There are a number of techniques that can be used to try to accomplish this. The first resort is usually complete bed rest. Maintaining a horizontal position reduces pressure on the cervix, which may allow it to stay lengthened longer, and avoiding unnecessary movement may reduce uterine irritation, which can lead to contractions. Likewise, proper nutrition and especially hydration are important: dehydration can lead to premature uterine contractions. In a hospital setting, an drug-free IV drip may be used to try to stop premature labor simply by improving the mother's hydration. Lastly, there are anti-contraction medications (tocolytics), such as ritodrine, fenoterol, nifedipine and atosiban.

Premature birth can not always be prevented. Severely premature infants may have underdeveloped lungs, because they are not yet producing their own surfactant. This can lead directly to Infant respiratory distress syndrome|Respiratory Distress Syndrome, also called hyaline membrane disease, in the neonate. To try to reduce the risk of this outcome, pregnant mothers are routinely administered at least one course of glucocorticoids, a steroid that easily passes the placental barrier and stimulates growth in the lungs of the fetus. Typical glucocorticoids that would be administered in this context are betamethasone or dexamethasone, often when the fetus has reached viability at 24 weeks. In cases where premature birth is imminent, a second "rescue" dose of steroids may be administered 12 to 24 hours before the anticipated birth. There is no research consensus on the efficacy and side-effects of a second dose of steroids, but the consequences of RDS are so severe that a second dose is often viewed as worth the risk.

Infants born more than 2 weeks prior to 40 weeks show physical signs of their prematurity and may develop other problems as well. Common problems in infants with severe to moderate prematurity (26 to 34 weeks) include jaundice, hypoglycemia, hypocalcemia, infant respiratory distress syndrome (IRDS), bronchopulmonary dysplasia (BPD), intracranial hemorrhage, retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC) and rickets.

The earliest gestational age at which the infant may survive is referred to as the limit of viability. As NICU care has improved over the last 40 years, the limit of viability has declined to about 25 weeks (400-500 grams). As risk of brain damage and developmental delay is significant at that threshold even if the infant survives, there are medical ethics|ethical controversies over the aggressiveness of the care rendered to such infants. The limit of viability has also become a factor in the abortion debate.

The required care for premature infants differs greatly depending on the child's gestational age, birth weight, and overall maturity. Measures common among extremely premature infants include:

• Placing the infant in a warmer or isolette. Premature infants are easily susceptible to infection, and preventing this is a key priority.

Adjustment after preterm birth for parents can be very difficult. The NICU setting is foreign and often intimidating and scary. Additionally, parents often have difficulty becoming involved in their child's care because of the NICU setting. This affects the parents transition into parenthood because they are unable to fulfill their expected roles. Furthermore, often premature birth is accompanied by a difficult NICU course and therefore parents are forced to confront difficult decisions about their child's care.
Studies have shown that the transition to parenthood for parents of preterm infants follows a different and longer course than that of parents with term infants.

In a study by Jackson et al (2003)ref|1 researchers found that both mothers and fathers travel a course from alienation to responsibility to confidence to familiarity in approximately the first 18 months of the child's life.

In a separate study by McHaffieref|2, researchers found that parents of very low birth weight infants (<1500g) follow a similar but slightly different course, likely because their infants tend to be more in peril. Mothers travel from anticipatory grief to anxious waiting to positive anticipation while the infant is in the NICU. After discharge the mother travels from anxious adjustment to exhausted accommodation to confident caring, usually within the first three months following discharge.

• note|1 Jackson K, Ternestedt BM, Schollin J. From alienation to familiarity: experiences of mothers and fathers of preterm infants. J Adv Nurs 2003;43:120-9. PMID 12834369

• Childbirth

• http://www.shareyourstory.org Share Your Story: A community for parents of preemies

• http://www.marchofdimes.com March of Dimes Web site: http://marchofdimes.com/prematurity

Last Modified:   2005-12-23