premature infant Alternative Names
prematurity, preterm births, low-birth-weight infant
A premature infant is a baby who is born more than 3 weeks early. Babies who have spent less than 37 weeks completed in the womb are considered premature.
What is going on in the body?
Premature babies have not developed completely. The earlier a baby is born, the less developed its organs are. Premature babies tend to have very specific problems. These are related to having underdeveloped organs and the treatments that they receive for this. For example, a baby born after only 24 weeks in the womb cannot breathe well on its own because its lungs are not developed enough. It will probably need the help of an artificial breathing machine, or ventilator, for several weeks, or even months.
What are the signs and symptoms of the condition?
Aside from how early a baby is born, the baby's weight at birth can help predict how well the baby will do. Babies born weighing less than 2500 grams (about 5.5 pounds) are called low-birth-weight, or LBW, infants. LBW babies make up only 7% of births, but they account for two-thirds of newborn deaths. Babies who weigh less than 1500 grams (about 3.25 pounds) are called very-low-birth-weight, or VLBW, infants. These babies make up about 1% of births, but account for half of newborn deaths.
There are many problems associated with being born early. One of the problems premature babies can have is respiratory distress syndrome. This occurs when the baby's lungs are too underdeveloped to work properly. A baby with immature lungs may have trouble breathing and need a breathing tube and ventilator. Some babies cannot get enough oxygen, even with a ventilator. The ventilator can sometimes cause damage to the lungs. If high levels of oxygen have to be used, the baby can develop eye problems.
Another problem is that these babies have underdeveloped immune systems. That means they are not very good at fighting infection. They can develop severe and sometimes fatal infections, such as group B streptococcal septicaemia, more easily than a normal newborn. Extremely premature babies usually need to be given antibiotics often and for long periods of time. Some of the antibiotics can cause long-term problems.
When babies are born very early, they can have bleeding in their brains. This can cause mild to severe brain damage. Many extremely premature babies do not develop normally as they grow up. It is hard to predict while they are still in the hospital which babies will have development problems.
Premature babies can also have problems in the gut, the kidneys, or the liver. They can have trouble controlling the level of sugars and salts in their blood stream. They often develop anaemia, and sometimes need blood transfusions to treat it.
What are the causes and risks of the condition?
Certain factors in the mother are linked with the birth of a low-birth-weight infant. These factors include:
Some babies have factors themselves that make them more likely to be born early. These factors include multiple babies in the same womb, such as twins or triplets. The baby may have physical problems or an infection.
- a previous low-birth-weight infant
- no antenatal care
- fewer years of schooling
- age less than 16 years or more than 35 years
- cigarette smoking
- alcohol use
- drug abuse or addiction
- being single
- short time between pregnancies
- being very thin before pregnancy (less than 45 kg)
- poor weight gain during pregnancy (less than 4.5 kg)
- African-American ancestry
Sometimes the mother's womb itself has problems. The placenta may not be adequate to support the baby full term. The placenta may be in an unusual location, such as placenta praevia. When the mother has a chronic illness like diabetes, heart disease such as congestive heart failure, or high blood pressure, she is more likely to deliver early. Certain infections in the mother, such as genital herpes or syphilis, can cause the baby to be born early.
What can be done to prevent the condition?
Mothers may be able to lessen the chances of premature birth by avoiding some of the risk factors. For example, antenatal care may help prevent a mother from having a premature baby. But sometimes there is no way to prevent a baby from being born early.
How is the condition diagnosed?
Usually, a woman knows how many weeks she has been pregnant. There are other ways to tell the age of the baby. The growth of the unborn baby can be estimated by examining the pregnant woman's womb. Ultrasound, a test that uses sound waves, can also be used to estimate the age of the unborn baby. After the baby is born, the doctor can estimate the baby's age by doing a physical examination.
What are the long-term effects of the condition?
Sometimes premature babies grow to be completely normal children. Over 90% of infants weighing more than 1500g (about 3 pounds) survive. But only about 40% of infants weighing less than 750g (about 1.5 pounds) survive.
Of the babies who survive, 10% to 25% have mild developmental problems. Severe developmental problems occur in 5% to 10% of these babies. The smaller a baby is at birth, the more likely the baby is to have problems. The chronic problems that premature babies can develop often depend on what happens in the first few months after birth.
Premature birth or LBW also carries a higher risk of cerebral palsy and mental retardation. These babies can develop seizures or convulsions. VLBW infants may have problems with learning and school performance. The majority are able to attend regular school.
- If a baby needs to be on a ventilator for a long time, long term breathing problems can result. Being chronically ill makes it hard for these infants to grow normally.
- If a baby is extremely premature, 25 weeks or less and affected by a condition called retinopathy of prematurity (ROP), laser treatment is sometimes required.
- If a baby is on certain types of antibiotics, trouble with hearing can develop, although this is very unusual as blood levels of these antibiotics are measured carefully.
What are the risks to others?
Parents often do not realize all the problems that premature babies can have. It's hard for the family to deal with the baby being in the hospital for a long time. The difficulty of predicting long-term effects can be very stressful.
What are the treatments for the condition?
Treatment depends on how early a baby is born and its weight at birth. Babies who are born only a few weeks early usually just need time to grow, and time to learn to feed well. They often go home after a short time in the hospital. Usually, the earlier a baby is born, the longer it will stay in the hospital and the more treatment it will need. The earlier a baby is born, the less likely it is to survive even with the best of care. The very premature babies who do survive often have to stay in a specialised hospital for several months.
What happens after treatment for the condition?
Once the baby is able to breathe on its own, he or she will usually spend some time in the nursery to grow more before going home. When the baby is feeding well he/she can go home and the parents can try to resume a normal life. But the baby may still need more care than a baby born on time. During the first year, the parents may spend more time in doctor visits with their baby than parents of babies born on time.
How is the condition monitored?
Babies who are born early usually are carefully monitored, especially for the first year. The earlier they are born, the more treatment they have to go through, and the more care they'll have after leaving the hospital. Very premature babies will be seen by eye and hearing specialists. They will be taken care of by paediatricians, development specialists and breathing specialists. Teams of doctors work together to give these babies as much care as they need to help them develop as normally as possible.
Author: Lama Rimawi, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request