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Premature Infant

Premature Infant

Alternate Names

  • prematurity
  • preterm birth


A premature infant is a baby who has spent less than 37 weeks in the womb. The average length of pregnancy is 40 weeks. Thus, a premature infant is one who is born 3 weeks or more before the due date.

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 are at risk for certain specific problems related to their underdeveloped organs. .For example, the lungs of a baby born after only 24 weeks in the womb are not yet fully developed. Therefore, the baby cannot breathe well on its own and will probably need the help of an artificial breathing machine, or ventilator.
Sometimes the treatments that they receive for their underdeveloped organs can lead to complications of their own. An example of this is the damage to the retinas of a premature baby's eyes, that can be caused by excess oxygen.


What are the causes and risks of the condition?

Mothers with certain risk factors are statistically more likely to give birth to a low-birth-weight infant. These factors include the following:
  • abusing drugs or being addicted to drugs
  • being single
  • being very thin, or less than 100 pounds, before pregnancy
  • being younger than 16 years of age or older than 35 years of age
  • dealing with high levels of stress
  • having already given birth to a low-birth-weight infant
  • having African American ancestry
  • having had few years of schooling
  • having poor weight gain, or less than a 10-pound gain, during pregnancy
  • living in poverty
  • receiving no prenatal care
  • smoking cigarettes
  • using alcohol
  • waiting only a short time between pregnancies
Some babies have factors themselves that make them more likely to be born early. These factors include being one of multiple babies in the same womb, such as twins or triplets. The baby may have physical problems or a bloodstream damaged by infection.
Sometimes there are problems with a mother's womb. The placenta may not be adequate to support the baby to full term. The placenta may be in an unusual location, such as near to or obstructing the outlet to the womb (placenta previa). When the mother has a chronic illness like diabetes, 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 also trigger a premature birth.


What can be done to prevent the condition?

Mothers may be able to lessen the chances of premature birth by avoiding some of the pregnancy risk factors. For example, prenatal care may help prevent a mother from having a premature baby. It is important to avoid drugs, alcohol, and smoking during pregnancy. 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. The healthcare provider measures the size of pregnant woman's womb to help confirm the dates, but if there is any doubt, the best information is obtained from a pregnancy ultrasound . This test uses high frequency sound waves - much safer than X-ray for the unborn infant - to measure the size of the baby's head and look for other indicators of development. After the baby is born, the healthcare provider can estimate the baby's age by doing a physical exam.

Long Term Effects

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 1,500 grams, or about 3 pounds, survive. The rate decreases to 40% for infants weighing less than 750 grams, or about 1.5 pounds. Of the babies who survive, severe developmental problems occur in 5% to 10% and mild developmental problems in another 10 to 25%. The smaller a baby is at birth, the more likely the baby is to have serious difficulties. Whether the baby's initial hurdles turn into long term issues depends in large part on what happens in the first few months after birth.
  • If a baby needs to be on a ventilator for a long time, lifelong breathing problems can result. Being chronically ill makes it hard for these infants to grow normally.
  • If a baby needs high levels of oxygen, the eyes can be affected. Some of these babies become blind.
  • If a baby is on certain types of antibiotics, trouble with hearing can develop.
Premature birth or LBW also carries a higher risk of cerebral palsy and mental retardation. These babies can develop seizures as well. VLBW infants may have problems with learning and school performance.

Other Risks

What are the risks to others?

Being premature is, in and of itself, obviously not contagious and poses no risk to others. Some infectious conditions in the mother that may have resulted in a premature delivery, could be contagious.


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 very premature babies are least likely to survive even with the best of care, and those who do survive often have to stay in a specialized hospital for several months.

Side Effects

What are the side effects of the treatments?

Ventilators may damage the baby's lungs. They also may cause chronic breathing problems. High levels of oxygen are sometimes needed to make sure the baby's organs get enough. This can have the side effect of damaging the blood vessels in the eyes. This in turn can cause poor vision. Certain antibiotics can cause trouble with hearing as the baby grows. Very premature babies often need to be fed through the bloodstream instead of through their guts. These babies can develop liver injury as a result.

After Treatment

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 reaches a certain weight, the baby 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 full term babies.


How is the condition monitored?

Babies who are born early usually are carefully monitored, especially for the first year. Very premature babies will be seen by eye and hearing specialists. They will be taken care of by development specialists and breathing specialists. Teams of healthcare providers work together to give these babies as much care as they need to help them develop as normally as possible. Any new or worsening symptoms should be reported to the healthcare provider.


Nelson's Essentials of Pediatrics, RE Behrman and RM Kliegman, 1994, pp. 157-215.

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