What is Premature labor?

The normal gestation period for a fetus is approximately 39 weeks. Any child born before the 37^th week of gestation is considered premature, according to the March of Dimes Birth Defects Foundation. This date is calculated based on the first day of the woman's last menstrual period and confirmed by ultrasound. It is essential to establish an accurate date of a pregnancy to diagnose a premature birth. Without the additional time in the mother's womb to develop and mature, the baby is at a higher risk of medical and developmental complications.

The most common complication of premature birth is underdeveloped lungs, which is typically referred to as respiratory distress syndrome (RDS). In addition, premature birth is the leading cause of neonatal death during the first month of life. There are several factors that greatly impact the premature baby's chances of survival and potential developmental challenges. These factors include:

• The baby's gestational age (the number of weeks of pregnancy that have been completed)
• The baby's weight
• Whether the baby has respiratory difficulties
• Whether the baby has any birth defects
• Whether the baby has any severe illnesses or infections

Although there have been many advances in obstetrics, the rate of premature births in the United States has not dropped in more than 40 years, but has increased somewhat, according to the American College of Obstetricians and Gynecologists (ACOG).

In 2004, just over 4 million births were recorded by the Centers for Disease Control and Prevention (CDC). Over ½ million infants were born prematurely during that year – the highest number reported since 1981. The preterm birth rate rose two percent than the previous year to 12.5 percent, or one out of every eight live births. Although overall preterm birth rates increased for the non-Hispanic white and Hispanic populations, the highest rate of premature deliveries was found among the non-Hispanic black population at 17.8 percent.

In a baby's first month of life, prematurity is the leading cause of death and disability, according to the March of Dimes. Premature labor results in one-third of all infant deaths in the United States, according to the CDC. In addition, the organization reports that deliveries of premature babies (or “preemies”) cost nearly 15 times more than deliveries of full-term babies. A primary reason is the length of hospitalization required for preemies. These babies are often hospitalized for days or weeks, compared to the average two to three days for a healthy, full-term infant.

Most full-term babies weigh an average of about 7 pounds at birth. This is a sharp contrast to preemies, who can weigh 5 pounds or even less. Premature babies exhibit certain physical characteristics. The more premature a baby is, the smaller the baby will be and the larger the head will appear in relation to the rest of the body.

Preemies also have less fat, which results in their skin appearing thinner and more transparent, making it possible to see the underlying blood vessels. The reduced fat means that the baby has less protection from cold or even normal temperatures. For this reason, most premature babies are placed in an incubator, which is an enclosed, climate-controlled bed that helps keep the baby warm.

Preemies are at risk for health problems, many of which are serious. However, those born between 32 and 36 weeks (84 percent of preemies) may have few or no complications, according to the March of Dimes. Those born earliest experience the greatest risk of complications, long-term disabilities and death. For extremely premature babies, the risk of mental retardation, cerebral palsy, lung and gastrointestinal problems and vision or hearing loss is much higher. Advances in the treatment of these tiny newborns during the past decade have improved the chances for survival, and helped to reduce some of the complications that may accompany early arrival.

Diagnosis and treatment for premature birth

In general, an obstetrician-gynecologist (ObGyn) will be more aggressive in attempts to delay labor when the patient is less than 32 weeks pregnant. If a physician orders the patient to the hospital, an examination of the cervix will help determine if the cervix is opening (dilating), which could indicate labor has begun. The physician will also check to see if fetal membranes have ruptured. Monitors are typically placed on the patient's abdomen to measure the baby's heart rate, and observe possible uterine contractions.

Some ObGyns may order a fetal fibronectin test (fibronectin is a protein that attaches the sac that holds the fetus to the uterus). This test requires that a sample be taken of the cervical and vaginal secretions. Most women consider it about as uncomfortable as a Pap smear. Though the results will not definitively determine if a woman has begun premature labor, it will clearly indicate if she has not begun labor. A negative test result means that it is highly unlikely that the woman will give birth within the next seven to 14 days, and can help the physician decide whether to delay giving medications to stall preterm labor.

Other tests might include a urine test, to exclude a urinary tract infection as a cause of preterm labor, or an amniocentesis, which can offer information about the baby's lung development. Additional samples from the cervix may be tested for infection, which is a major cause of premature labor. If preterm labor is determined, initial treatment will most often include hydration with or without administration of terbutaline. If this is unsuccessful in stopping labor, further treatment may include the intravenous administration of magnesium sulfate. An initial large dose, which may cause nausea, is followed by lower dose continuous intravenous administration over a period of 12 to 24 hours or more.

If labor continues to progress, and the patient is between 24 and 34 weeks gestation, a corticosteroid may be given to the woman by injection 24 hours before birth in order to increase the baby's lung and brain development. Hospitals that have neonatal intensive care units (NICUs) offer premature babies the best chance for optimal health and survival. If premature labor continues and a premature delivery is expected, the patient may be transferred to a hospital with an NICU. Depending on how premature the labor is, the ObGyn may call in a neonatologist, a physician who specializes in premature intensive care. The neonatologist can help determine if any additional treatments are necessary for the premature infant.

Many infants born before 37 weeks of gestation will have respiratory distress syndrome (RDS). RDS is one of the most common complications associated with premature delivery. If left untreated, severe cases can lead to multiple organ failure and even death.

Treatment of RDS includes placing the baby on a respirator, which is a machine that helps the baby to breathe. In addition, the neonatologist may order oxygen treatments or treatments that include nitric oxide to improve breathing. In many cases, RDS usually resolves within four or five days. Additional treatment of a pulmonary surfactant, which keeps small air sacs in the lungs from collapsing, can help to speed recovery. In some cases, RDS can be avoided if labor can be delayed by 24 to 48 hours and specific medications (e.g., steroids) are administered to the mother to allow an accelerated development of the lungs.

Another common complication of premature infants and a serious concern for parents and physicians is bleeding in the brain (intracranial hemorrhage). This happens more often in very premature babies (before 34 weeks gestation), who are at higher risk of serious complications and conditions.

In addition to RDS and intracranial hemorrhage, other common complications that impact premature babies more often than full-term babies include:

• Low birth weight (less than 2,500 grams or about 5 pounds, 8 ounces)
• Very low birth weight (less than 1,500 grams or about 3 pounds, 5 ounces)
• Eye problems (retinopathy of prematurity)
• Intestinal problems
• Breathing problems (apnea)
• Jaundice (a yellow skin color due to an immature liver)
• Anemia (lack of red blood cells)
• Infections
• Sudden infant death syndrome (SIDS)

Prevention methods for premature labor

Although there are identifiable risk factors that indicate a woman is more likely to deliver prematurely, there are no known methods of prevention. Perhaps the most important way to lower the risk of a premature birth is to get early and adequate prenatal care.

Another way for women to prevent many pregnancy complications is to maintain a healthy weight and lifestyle. In addition, consuming the recommended amount of prenatal vitamins, including folic acid, may reduce the risk of premature birth, as well as birth defects and other complications.

Although bed rest, fluids and labor-inhibiting medications including steroids may be prescribed, these attempts often merely offer a short delay in the delivery to allow physicians to speed the development of the baby's lungs and, if necessary, transfer the mother to a hospital that is better equipped for premature babies, such as one with a neonatal intensive care unit (NICU).

Medications

Proventil (Albuterol), Decadron (Dexamethasone)

What might complicate it?

Complications include infection, increased morbidity and mortality of the premature infant, and hemorrhage.

Predicted outcome

Most cases (70%) of premature labor can be successfully stopped with only bedrest. About 25% of cases will require the administration of drugs to stop the labor. If labor cannot be stopped, a premature infant will be delivered.

Alternatives

This could be "false labor" (Braxton Hicks' contractions).

Appropriate specialists

Obstetrician or gynecologist, perinatologist, and pediatrician.

Last updated 3 July 2015