Many babies are born before their mother’s pregnancy has reached full-term. This can lead to health problems – although most go on to lead active and fulfilling lives. BBC News Online examines the risks associated with a premature birth.
How is prematurity defined?
Most babies are fully developed and ready for within one or two weeks of their estimated due date, so a full term pregnancy is defined as anything between 38-42 weeks of gestation. Babies born before 38 weeks gestation – about 10% of the total – are considered premature.
Are premature babies likely to survive?
Yes. The outlook for premature infants has improved dramatically in recent years. Even babies born as early as 25 weeks now have a good chance of surviving. More than 90% of premature babies who weigh 800 grams (a little less than two pounds) or more survive. Those who weigh more than 500 grams (a little more than 1 pound) have a 40% to 50% chance of survival.
Are premature babies at risk?
Premature babies have less time to fully develop and build strength in the womb. As a result they’re often at increased risk of medical and developmental problems. But the risks largely depend on just how early a baby is born.
Many babies born between 35 and 38 weeks gestation may be able to eat well and maintain their body temperature well on their own. However, they are more likely than full-term babies to have problems with feeding and, because they lack the necessary body fat, temperature control.
They are also at higher risk of developing difficulties with their breathing because their lungs are underdeveloped. In addition, they may be less able to cope with infections or other illnesses. They are also prone to anaemia and low blood pressure. Jaundice is a common condition in premature babies, caused by the build up of a compound called bilirubin. This causes a yellow discoloration of the skin and the whites of the eyes, and is usually mild, and easily treatable. However, high levels of bilirubin can cause brain damage.
The shorter the time of gestation, the higher the risk of complications following birth. A baby born at 25 weeks almost always has breathing and temperature control problems.
How are premature babies treated?
Extremely premature babies are likely to be on a ventilator to aid their breathing artificially – sometimes for months. Most premature babies will be placed in an incubator on a special neo-natal unit. Incubators are made of transparent plastic, and they completely surround an infant to keep him warm, decrease the chance of infection, and limit water loss.
Breast milk is an excellent source of nutrition, but premature infants are too immature to feed directly from the breast or bottle until at least 32 weeks after conception. Most premature infants have to be fed slowly because of the risk of developing an intestinal infection called necrotizing enterocolitis (NEC).
Breast milk can be pumped by the mother and fed to the premature baby through a tube that goes from the baby’s nose or mouth into the stomach. Special fortifiers may be added to the milk that a premature baby receives, because they often have higher vitamin needs than full-term infants.
What is the long-term outlook?
About half of babies born at 25 weeks will have learning difficulties, and/or problems with their eyesight and hearing.
The eyes of premature infants are especially vulnerable to injury after birth. They are at heightened risk of a complication called retinopathy of prematurity , which is caused by abnormal growth of blood vessels in the eye. Extremely premature babies may also have problems growing. They also seem to be more likely to develop asthma. Children born at a later stage of pregnancy are much less likely to develop long-term problems.
What causes a premature birth?
In most cases the cause of premature labour is unknown. However, it can be linked to medical complications developed by the mother. Other factors may include maternal stress, and infection.
Lifestyle factors such as smoking, drug use, drinking alcohol and a poor diet have all been linked to an increased risk of pre-term birth.
Three groups of women are known to be at risk of giving birth prematurely:
# Women who are pregnant with twins, triplets or more
# Women who have had a previous preterm birth
# Women with certain uterine or cervical abnormalities
10th Nov 2007