A baby born before 37 weeks of pregnancy is considered premature, that is, born before complete maturity. Slightly fewer than 12 percent of all babies are premature. Overall, the rate of premature births is rising, mainly due to the large numbers of multiple births in recent years. Twins and other multiples are about six times more likely to be premature than single birth babies. The rate of premature single births is slightly increasing each year.
According to the National Center for Health Statistics, about 13 percent of babies born in the U.S. are born preterm, or before 37 completed weeks of pregnancy. Of all babies:
- About 9 percent are born between 34 and 36 weeks of gestation (the time from conception to birth)
- About 1.6 percent are born between 32 and 33 weeks of gestation
- About 1.2 percent are born between 28 and 31 weeks of gestation
Other terms often used for prematurity are preterm and "preemie." Many premature babies also weigh less than 2,500 grams (5.5 pounds) and may be referred to as low birthweight (LBW).
Premature infants born between 34 and 37 weeks of pregnancy are often called late preterm or near-term infants. Late preterm infants are often much larger than very premature infants but may only be slightly smaller than full-term infants.
Late preterm babies usually appear healthy at birth but may have more difficulties adapting than full-term babies. Because of their smaller size, they may have trouble maintaining their body temperature. They often have difficulty with breastfeeding and bottle feeding, and may need to eat more frequently. They usually require more sleep and may even sleep through a feeding, which means they miss much-needed calories.
Late preterm infants may also have breathing difficulties, although these are often identified before the infants go home from the hospital. These infants are also at higher risk for infections and jaundice, and should be watched for signs of these conditions. Late preterm infants should be seen by a care provider within the first one or two days after going home from the hospital.
There are many factors linked to premature birth. Some directly cause early labor and birth, while others can make the mother or baby sick and require early delivery. The following factors may contribute to a premature birth:
- Maternal factors:
- Preeclampsia (high blood pressure of pregnancy, also known as toxemia or gestational hypertension)
- Chronic medical illness (such as heart or kidney disease)
- Infection (such as group B streptococcus, urinary tract infections, vaginal infections, infections of the fetal/placental tissues)
- Drug use (such as cocaine)
- Abnormal structure of the uterus
- Cervical incompetence (inability of the cervix to stay closed during pregnancy)
- Previous preterm birth
- Factors involving the pregnancy:
- Abnormal or decreased function of the placenta
- Placenta previa (low lying position of the placenta)
- Placental abruption (early detachment from the uterus)
- Premature rupture of membranes (amniotic sac)
- Polyhydramnios (too much amniotic fluid)
- Factors involving the fetus:
- When fetal behavior indicates the intrauterine environment is not healthy
- Multiple gestation (twins, triplets or more)
Premature babies are born before their bodies and organ systems have completely matured. These babies are often small, with low birthweight (less than 2,500 grams or 5 ½ pounds), and they may need help breathing, eating, fighting infection, and staying warm. Very premature babies, those born before 28 weeks, are especially vulnerable. Many of their organs may not be ready for life outside the mother's uterus and may be too immature to function well.
Some of the problems premature babies may experience include:
- Temperature instability--inability to stay warm due to low body fat.
- Respiratory problems:
- Hyaline membrane disease/respiratory distress syndrome--a condition in which the air sacs cannot stay open due to lack of surfactant in the lungs.
- Chronic lung disease/bronchopulmonary dysplasia--long-term respiratory problems caused by injury to the lung tissue.
- Air leaking out of the normal lung spaces into other tissues
- Incomplete lung development
- Apnea (stopping breathing)--occurs in about half of babies born at or before 30 weeks
- Patent ductus arteriosus (PDA)--a heart condition that causes blood to divert away from the lungs.
- Too low or too high blood pressure
- Low heart rate--often occurs with apnea
- Blood and metabolic:
- Anemia--may require blood transfusion
- Jaundice--due to immaturity of liver and gastrointestinal function
- Too low or too high levels of minerals and other substances in the blood such as calcium and glucose (sugar)
- Immature kidney function
- Difficulty feeding--many are unable to coordinate suck and swallow before 35 weeks gestation
- Poor digestion
- Necrotizing enterocolitis (NEC)--a serious disease of the intestine common in premature babies.
- Intraventricular hemorrhage--bleeding in the brain.
- Periventricular leukomalacia--softening of tissues of the brain around the ventricles (the spaces in the brain containing cerebrospinal fluid).
- Poor muscle tone
- Seizures--may be due to bleeding in the brain
- Retinopathy of prematurity--abnormal growth of the blood vessels in a baby's eye.
- Infections--premature infants are more susceptible to infection and may require antibiotics
Premature babies can have long-term health problems as well. Generally, the more premature the baby, the more serious and long lasting are the health problems.
The following are the most common characteristics of a premature baby. However, each baby may show different characteristics of the condition. Characteristics may include:
- Small baby, often weighing less than 2,500 grams (5 pounds 8 ounces)
- Thin, shiny, pink or red skin, able to see veins
- Little body fat
- Little scalp hair, but may have lots of lanugo (soft body hair)
- Weak cry and body tone
- Genitals may be small and underdeveloped
The characteristics of prematurity may resemble other conditions or medical problems. Always consult your baby's doctor for a diagnosis.
Specific treatment for prematurity will be determined by your baby's doctor based on:
- Your baby's gestational age, overall health, and medical history
- Extent of the disease
- Tolerance for specific medications, procedures, or therapies
- Expectations for the course of the disease
- Your opinion or preference
Treatment may include:
- Prenatal corticosteroid therapy
One of the most important parts of care for premature babies is a medication called a corticosteroid. Research has found that giving the mother a steroid medication at least 48 hours prior to preterm delivery greatly reduces the incidence and severity of respiratory disease in the baby. Another major benefit of steroid treatment is lessening of intraventricular hemorrhage (bleeding in the baby's brain). Although studies are not clear, prenatal steroids may also help reduce the incidence of NEC and PDA. Mothers may be given steroids when preterm birth is likely between 24 and 34 weeks of pregnancy. Before that time, or after, the medication usually is not effective.
Premature babies usually need care in a special nursery called the Neonatal Intensive Care Unit (NICU). The NICU combines advanced technology and trained health professionals to provide specialized care for the tiniest patients. The NICU team is led by a neonatologist, who is a pediatrician with additional training in the care of sick and premature babies.
Care of premature babies may also include:
- Temperature-controlled beds
- Monitoring of temperature, blood pressure, heart and breathing rates, and oxygen levels
- Giving extra oxygen by a mask or with a breathing machine
- Mechanical ventilators (breathing machines) to do the work of breathing for the baby
- Intravenous (IV) fluids--when feedings cannot be given, or for medications
- Placement of catheters (small tube) into the umbilical cord to give fluids and medications and to draw blood
- X-rays (for diagnosing problems and checking tube placement)
- Special feedings of breast milk or formula, sometimes with a tube into the stomach if a baby cannot suck. Breast milk has many advantages for premature babies as it contains immunities from the mother and many important nutrients.
- Medications and other treatments for complications, such as antibiotics
- Kangaroo Care--a method of caring for premature babies using skin-to-skin contact with the parent to provide contact and aid parent-infant attachment. Studies have found that babies who "kangaroo" may have shorter stays in the NICU.
Premature babies often need time to "catch up" in both development and growth. In the hospital, this catch-up time may involve learning to eat and sleep, as well as steadily gaining weight. Depending on their condition, premature babies often stay in the hospital until they reach the pregnancy due date.
If a baby was transferred to another hospital for specialized NICU care, he or she may be transferred back to the "home" hospital once the condition is stable.
Consult your baby's doctor for information about the specific criteria for discharge of premature babies at your hospital. General goals for discharge may include the following:
- Serious illnesses are resolved
- Stable temperature--able to stay warm in an open crib
- Taking all feedings by breast or bottle
- No recent apnea or low heart rate
- Parents are able to provide care including medications and feedings
Before discharge, premature babies also need an eye examination and hearing test to check for problems related to prematurity. Parents need information about follow-up visits with the pediatrician for baby care and immunizations. Many hospitals have special follow-up healthcare programs for premature and low birthweight babies.
Even though they are otherwise ready for discharge, some babies continue to have special needs such as extra oxygen or tube feedings. With instruction and the right equipment, these babies are often able to be cared for at home by parents. A hospital social worker can often help coordinate discharge plans when special care is needed.
Ask your baby's doctor about a "trial run" overnight stay in a parenting room at the hospital before your baby is discharged. This can help you adjust to caring for your baby while healthcare providers are nearby for help and reassurance. Parents may also feel more confident taking their baby home when they have been given instructions in infant CPR (cardiopulmonary resuscitation) and infant safety.
Premature infants are at increased risk for sudden infant death syndrome (SIDS) and should be sleeping on their back before being sent home from the hospital. Please talk with your infant's health care providers about these recommendations from the American Academy of Pediatrics (AAP) to reduce the risk for SIDS and other sleep-related infant deaths in infants from birth to age 1:
- Make sure your baby is immunized. An infant who is fully immunized can reduce his or her risk for SIDS by 50 percent.
- Breastfeed your infant. The AAP recommends breastfeeding for at least six months.
- Place your infant on his or her back for sleep or naps. This can decrease the risk for SIDS, aspiration, and choking. Never place your baby on his or her side or stomach for sleep or naps. If your baby is awake, allow your child time on his or her tummy as long as you are supervising, to decrease the chances that your child will develop a flat head.
- Always talk with your baby's doctor before raising the head of their crib if he or she has been diagnosed with gastroesophageal reflux.
- Offer your baby a pacifier for sleeping or naps, if he or she isn't breastfed. If breastfeeding, delay introducing a pacifier until breastfeeding has been firmly established.
- Use a firm mattress (covered by a tightly fitted sheet) to prevent gaps between the mattress and the sides of a crib, a play yard, or a bassinet. This can decrease the risk for entrapment, suffocation, and SIDS.
- Share your room instead of your bed with your baby. Putting your baby in bed with you raises the risk for strangulation, suffocation, entrapment, and SIDS. Bed sharing is not recommended for twins or other higher multiples.
- Avoid using infant seats, car seats, strollers, infant carriers, and infant swings for routine sleep and daily naps. These may lead to obstruction of an infant's airway or suffocation.
- Avoid using illicit drugs and alcohol, and don't smoke during pregnancy or after birth.
- Avoid overbundling, overdressing, or covering an infant's face or head. This will prevent him or her from getting overheated, reducing the risks for SIDS.
- Avoid using loose bedding or soft objects—bumper pads, pillows, comforters, blankets—in an infant's crib or bassinet to help prevent suffocation, strangulation, entrapment, or SIDS.
- Avoid using cardiorespiratory monitors and commercial devices—wedges, positioners, and special mattresses—to help decrease the risk for SIDS and sleep-related infant deaths.
- Always place cribs, bassinets, and play yards in hazard-free areas—those with no dangling cords or wires—to reduce the risk for strangulation.
Because of the tremendous advances in the care of sick and premature babies, more and more babies are surviving despite being born early and being very small. But prevention of early birth is the best way of promoting good health for babies.
Prenatal care is a key factor in preventing preterm births and low birthweight babies. At prenatal visits, the health of both mother and fetus can be checked. Because maternal nutrition and weight gain are linked with fetal weight gain and birthweight, eating a healthy diet and gaining weight in pregnancy are essential. Prenatal care is also important in identifying problems and lifestyles that can increase the risks for preterm labor and birth. Some ways to help prevent prematurity and to provide the best care for premature babies may include the following:
- Identifying mothers at risk for preterm labor
- Prenatal education of the symptoms of preterm labor
- Avoiding heavy or repetitive work or standing for long periods of time which can increase the risk of preterm labor
- Early identification and treatment of preterm labor
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