Birth is considered premature, or preterm, when it occurs before 37 weeks of gestation (development time in the womb).
Normal, full-term gestation is 37 to 42 weeks. Those final weeks in the womb are crucial for healthy weight gain and development of the baby’s vital organs. Late preterm babies (born at 35 to 37 weeks gestation) may look fully mature, but they still have greater risks of health problems than babies born full term.
Premature infants weigh much less than babies born full term. They also often have serious health problems that require a long stay in the hospital. They are cared for by specially trained physicians and nurses in a neonatal intensive care unit (NICU).
In the past, premature birth was the major cause of infant mortality in the United States. Today, the quality of neonatal care has greatly improved, and 90 percent of babies born as early as 28 weeks now survive. However, preterm birth is still the top cause of infant deaths worldwide, according to a 2010 study in published in the British medical journal Lancet. (Blencowe et al., 2012)
The prevalence of premature birth is high in the United States. According to the NYU Child Study Center, approximately 400,000 babies (8 to 10 percent) are born prematurely each year. About 15 percent of these are due to multiple pregnancies (twins, triplets, etc.). (NYU)
In many cases, the cause of premature labor cannot be identified. But there are certain health conditions in the mother that increase the risk of preterm labor.
A mother with any of the following conditions is more likely to deliver preterm:
- heart disease
- kidney disease
- high blood pressure
Pregnancy-related causes of preterm labor in the mother include:
- poor nutrition preceding and during pregnancy
- smoking during pregnancy
- cocaine or amphetamine use during pregnancy
- certain infections, such as urinary tract and amniotic membrane infections
- history of preterm deliveries
- weakened cervix and early dilation (cervical incompetence)
- preeclampsia after 20 weeks (elevated blood pressure and protein in the urine)
- abnormal uterus
- premature rupture of the placenta (placenta previa)
According to the March of Dimes, if the mother is young (16 years old or younger) or older (35 years old or older), she is more likely to deliver preterm. African Americans have a higher incidence, as do women who lack access to prenatal healthcare. (March of Dimes, 2010)
The earlier a baby is born, the higher its risk of brain damage, blindness, hearing loss, cerebral palsy, and developmental delays.
At birth, the premature infant may show these signs:
- trouble breathing
- low weight
- inability to maintain a constant body temperature
- lanugo (body hair)
- low body fat
- less activity than normal
- underdeveloped muscles
- problems feeding due to underdeveloped sucking/swallowing coordination
- transparent skin
- yellow skin (jaundice)
Premature infants are often born with life-threatening conditions. Some of these problems can be resolved through proper neonatal intensive care. Others can result in long-term disability or illness.
Common health problems at birth include:
- neonatal respiratory distress syndrome due to underdeveloped lungs
- brain hemorrhage (bleeding into the brain)
- damage in the white brain tissue
- pulmonary hemorrhage (bleeding in the lungs)
- pulmonary interstitial emphysema (too much air in the lung tissue)
- necrotizing enterocolitis (severe intestinal inflammation)
- hypoglycemia (low blood sugar)
- neonatal sepsis (blood infection)
- pneumonia (infection and inflammation of the lungs)
- patent ductus arteriosis (an unclosed hole in the aorta of the heart)
- anemia (insufficient red blood cells for transporting oxygen to tissues)
Premature infants undergo tests soon after birth and are continuously monitored during their hospital stay. Common tests include:
- cardiorespiratory monitoring (checks breathing and heart rate)
- chest X-ray (shows heart and lung development)
- blood tests to check glucose, calcium, and bilirubin levels (tests liver, endocrine, and digestive functions)
- blood gas analysis (checks blood oxygen levels)
If premature labor cannot be stopped, the healthcare team will prepare for a high-risk birth. The mother may go to a hospital that has an NICU to ensure the infant receives immediate care.
In the first days and weeks of the baby’s life, hospital care will focus on supporting and enhancing vital organ development. It may be weeks or months before the baby will be able to live without medical support.
The newborn will first be kept in a temperature-controlled incubator. Monitoring equipment will track the baby’s heart rate, breathing, and blood oxygen levels.
Many premature babies cannot eat through the mouth because sucking and swallowing coordination is underdeveloped. Vital nutrients are given in one of two ways: feeding through a vein (IV) until the baby can receive food through the stomach, or feeding through a tube inserted through the nose or mouth and into the stomach.
If the baby’s lungs are underdeveloped, there are several ways to supply oxygen. Depending on how well the infant can breathe on its own, one of these methods may be used:
- ventilator machine (through a tube inserted into the trachea)
- continuous positive airway pressure, or CPAP (through tubes in the nose)
- oxygen hood, if baby breathes normally through the nose and mouth
Generally, a premature infant can be released from the hospital when it can:
- eat by mouth
- breathe without support
- maintain body temperature and body weight
Often, there are long-term complications of premature birth. Developmental, medical, and behavioral problems can continue through childhood. Some cause permanent disabilities.
Common long-term problems associated with preterm birth include:
- vision loss or blindness
- mental and learning disabilities
- physical disabilities or delays
- delayed growth and poor coordination
- bronchopulmonary dysplasia (lung scarring from ventilation at birth)
In a large, long-term study of prematurely born children published in The New England Journal of Medicine in 2005, these findings were reported:
- At age 2.5 years:
50 percent had no disabilities
25 percent had some disabilities
25 percent had severe disabilities
- At age 6.5 years, 22 percent had severe disabilities, such as:
inability to walk due to cerebral palsy
very low cognitive ability
blindness or deafness
- At age 6.5 years, 24 percent:
had cerebral palsy, but were able to walk
had an IQ in the special-needs range
had less severe hearing and vision problems
- 34 percent of the children had mild problems, such as nearsightedness, and low to normal cognitive scores
- 20 percent of the children were normal, with no health or cognitive problems
The incidence of attention-deficit/hyperactivity disorder (ADHD) is higher in prematurely born children than in children born full-term. (Marlow, et al., 2005)
Premature birth should be avoided if possible. Getting good prenatal care reduces your chances of a premature birth. Other important habits and actions include the following:
- Eat a high quality diet before and during your pregnancy
- Drink lots of water every day
- Be in the best possible health when you get pregnant
- Stop smoking
- Do not abuse illicit or prescription drugs (especially cocaine or amphetamines)
- See the doctor as soon as you know you are pregnant
- Continue to get regular prenatal care until your baby is born
- Get specialized, high-risk pregnancy care, if needed
If you go into labor early, there are medications that can slow or stop labor if given early enough. If you have a history of premature births, progesterone hormone supplements can help prevent premature labor in some women. Corticosteroids can also help the baby’s lungs and brain mature more quickly during the final weeks in the womb.