A premature infant is a baby born before 37 weeks gestation.
Preterm infant; Preemie; Premie
Causes, incidence, and risk factors
At birth, a baby is classified as one of the following:
- Premature (less than 37 weeks gestation)
- Full term (37 to 42 weeks gestation)
- Post term (born after 42 weeks gestation)
If a woman goes into labor before 37 weeks, it is called preterm labor. Often, the cause of preterm labor is unknown. Multiple pregnancy (twins, triplets, etc.) makes up about 15% of all premature births.
Health conditions and events in the mother may contribute to preterm labor. Examples are:
- Heart disease
- Infection (such as a urinary tract infection or infection of the amniotic membrane)
- Kidney disease
Different pregnancy-related problems increase the risk of preterm labor:
- An "insufficient" or weakened cervix, also called cervical incompetence
- Birth defects of the uterus
- History of preterm delivery
- Poor nutrition right before or during pregnancy
- Preeclampsia -- the development of high blood pressure and protein in the urine after the 20th week of pregnancy
- Premature rupture of the membranes (placenta previa)
Other factors that make preterm labor and a premature delivery more likely include:
- African-American ethnicity (not related to socioeconomic status)
- Age (younger than 16 or older than 35)
- Lack of prenatal care
- Low socioeconomic status
- Use of tobacco, cocaine, or amphetamines
A premature infant's organs are not fully developed. The infant needs special care in a nursery until the organ systems have developed enough to sustain life without medical support. This may take weeks to months.
A premature infant will have a lower birth weight than a full-term infant. Common physical signs of prematurity include:
- Body hair (lanugo)
- Abnormal breathing patterns (shallow, irregular pauses in breathing called apnea)
- Enlarged clitoris (female infant)
- Problems breathing due to immature lungs (neonatal respiratory distress syndrome) or pneumonia
- Lower muscle tone and less activity than full-term infants
- Problems feeding due to difficulty sucking or coordinating swallowing and breathing
- Less body fat
- Small scrotum, smooth without ridges, and undescended testicles (male infant)
- Soft, flexible ear cartilage
- Thin, smooth, shiny skin, which is often transparent (can see veins under skin)
Not all premature babies will have these characteristics.
Signs and tests
The infant may have difficulty breathing and maintaining body temperature.
Common tests performed on a premature infant include:
- Blood gas analysis
- Blood tests to check glucose, calcium, and bilirubin levels
- Chest x-ray
- Continuous cardiorespiratory monitoring (monitoring of breathing and heart rate)
When premature labor develops and cannot be stopped, the health care team will prepare for a high-risk birth. The mother may be moved to a center that specifically cares for premature infants in, for example, a neonatal intensive care unit (NICU).
After birth, the baby is admitted to a high-risk nursery. The infant is placed under a warmer or in a clear, heated box called an incubator, which controls the air temperature. Monitoring machines track the baby's breathing, heart rate, and level of oxygen in the blood.
Infants are usually unable to coordinate sucking and swallowing before 34 weeks gestation. Therefore, the baby may have a small, soft feeding tube placed through the nose or mouth into the stomach. In very premature or sick infants, nutrition may be given through a vein until the baby is stable enough to receive all nutrition in the stomach. (See: Neonatal weight gain and nutrition)
If the infant has breathing problems:
- A tube may be placed into the windpipe (trachea). A machine called a ventilator will help the baby breathe.
- Some babies whose breathing problems are less severe receive continuous positive airway pressure (CPAP) with small tubes in the nose rather than the trachea. Or they may receive only extra oxygen.
- Oxygen may be given by ventilator, CPAP, nasal prongs, or an oxygen hood over the baby's head.
Nursery care is needed until the infant is able to breathe without extra support, feed by mouth, and maintain body temperature and a stable or increasing body weight. In very small infants, other problems may complicate treatment and a longer hospital stay may be needed.
There are multiple support groups for parents of premature babies. Ask the social worker in the neonatal intensive care unit.
Prematurity used to be a major cause of infant deaths. Improved medical and nursing techniques have increased the survival of premature infants. The longer the pregnancy, the greater the chance of survival. Of babies born at 28 weeks, at least 90% survive.
Prematurity can have long-term effects. Many premature infants have medical, developmental, or behavioral problems that continue into childhood or are permanent. The more premature an infant and the smaller the birth weight, the greater the risk of complications. However, it is impossible to predict a baby's long-term outcome based on gestational age or birth weight.
Possible complications that may occur while in the hospital include:
- Bleeding into the brain (intraventricular hemorrhage of the newborn) or damage to the brain's white matter (periventricular leukomalacia)
- Infection or neonatal sepsis
- Low blood sugar (hypoglycemia)
- Neonatal respiratory distress syndrome, extra air in the tissue of the lungs (pulmonary interstitial emphysema), bleeding in the lungs (pulmonary hemorrhage)
- Newborn jaundice
- Patent ducturs arteriosus
- Severe intestinal inflammation (necrotizing enterocolitis)
Possible long-time complications include:
- Bronchopulmonary dysplasia (BPD)
- Delayed growth and development
- Mental or physical disability or delay
- Retinopathy of prematurity, vision loss, or blindness
Calling your health care provider
Call your health care provider if you are pregnant and believe you are going into labor prematurely.
If you are pregnant and not receiving prenatal care, call your health care provider or your state's department of health. Most state health departments have programs that provide prenatal care to mothers, whether or not they have insurance or are able to pay.
One of the most important steps to preventing prematurity is to receive prenatal care as early as possible in the pregnancy, and to continue such care until the baby is born. Statistics clearly show that early and good prenatal care reduces the chance of premature birth.
Premature labor can sometimes be treated or delayed by a medication that blocks uterine contractions. Many times, however, attempts to delay premature labor are not successful.
Betamethasone (a steroid medication) given to mothers in premature labor can reduce the severity of some of the prematurity complications on the baby.
Reviewed By: Kimberly G. Lee, MD, MSC, IBCLC, Associate Professor of Pediatrics, Division of Neonatology, Medical University of South Carolina, Charleston, SC. Review Provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.