By medical definition a premature baby is one that weighs less than 2-5 kg. The weight, of the baby does not accurately reflect the duration of pregnancy, although low weight is nearly always associated with delivery that occurs several weeks before the expected date. It should be emphasized that the chances of a baby surviving are related to the duration of pregnancy and not to its weight alone.
A small but mature baby stands a much better chance of surviving than does a large baby delivered unduly early. In most countries the diagnosis is based on low birth weight alone, but this is not an entirely satisfactory definition because it does not take into account the maturity of the baby. Low birth weight may be associated with postmaturity in which instance the baby would have a very good chance of survival.
A total of 750,000 births occur in the United Kingdom each year, of which approximately 50,000 or 7 per cent, are premature. A normal premature baby is supposed to be more intelligent than its fully mature siblings. This has never been disproved and could easily be true. Winston Churchill is always quoted as being the classic example.
The main causes of prematurity are ill understood and indeed in approximately 40 per cent of instances the exact cause is unknown. Various factors are, however, associated with prematurity, amongst the most important of which are pre-eclampsia, multiple pregnancy, premature rupture of the membranes, abnormalities of the placenta (such as placenta praevia and abruptio placentae), as well as maternal disease, malnutrition, anaemia and overwork. Other factors which may play a part are congenital abnormalities of the uterus, uterine fibroids and ovarian cysts.
Premature labour usually begins without any previous warning, the first sign being either premature rupture of the membranes, the onset of uterine contractions or some vaginal bleeding. Premature labour frequently occurs in.what has been an otherwise normal pregnancy in a woman who is pregnant for the first time. Once labour has started there is little that can be done, or indeed probably little that should be done, to stop its progress. However, in women who are less than 34 weeks pregnant attempts may be made to stop the labour progressing by giving sedatives or hormones, or by giving special drugs such as salbutamol or alcohol by means of an intravenous drip. If labour is stopped by one of these methods the woman has to remain in bed resting for several days or even weeks, the time varying with the cause of onset of labour.
If labour progresses it is usually shorter and easier than labour at term. The skull of the premature baby is softer than that of a mature baby as the skull bones have not completely developed, with the result that the premature skull is liable to injury at the time of delivery. It is, therefore, common practice to perform an episiotomy and protect the head from excessive pressure changes by a forceps delivery. Epidural anaesthesia may be recommended so that gentle forceps delivery can be painlessly performed and so that no drugs that might depress the baby’s respiration need by given.
The Premature Baby
Causes of Prematurity
Although in the majority of instances the cause of prematurity is not fully understood, it is certain that increasingly effective antenatal care and higher social standards in this country have greatly reduced the numbers of premature babies. Social and economic status is an important factor in prematurity, because the incidence is considerably higher in the lower income groups than in the professional and salaried’classes. Other related factors are inadequate or lack of antenatal care, poor living standards and illegitimate births. Maternal disease may also be a cause of prematurity, for example pre-eclampsia, antepartum haemorrhage or medical conditions such as diabetes mellitus, pre-existing hypertension and chronic nephritis. Maternal age must also be considered because the lowest incidence occurs in age groups 20 to 25 years and a high percentage occurs under the age of 20 years, perhaps because the younger age group contains most of the illegitimate births. Multiple pregnancies frequendy begin labour prematurely so that twins or triplets are usually of low birth weight.
Signs of Prematurity
The premature baby’s skin is red, wrinkled and covered with fine hair. His head is small but appears large in proportion to his body and the skull bones are soft. His eyes stay closed; his sucking reflex is poor. His heat regulating mechanism is poorly developed so that he can easily become chilled. The development of the respiratory centre in the brain is immature and the respiratory muscles are not well developed so that premature babies are liable to have difficulty in breathing. They have poor resistance to infections and these arc easily contracted. The premature baby sleeps more or less continuously and his cry is infrequent and feeble.
Care of the Premature Baby
Premature babies are usually nursed in a thermostatically controlled incubator to maintain their body temperature. The baby can, in these ideal circumstances, be nursed without clothes, making observations of colour and breathing more easy for the nursing staff. Oxygen can be administered more easily should it be necessary. Infections can be avoided by isolation and to a certain extent this is achieved by the incubator itself. The premature baby is handled as little as possible and therefore he is not bathed after delivery until his condition is satisfactory. Feeding is always a problem because premature babies require a high protein and a high carbohydrate intake if they are to gain weight adequately and because they lose quite a lot of weight in the first week of life. It is common practice to start feeding as early as possible. The method of feeding depends on the baby’s condition. If he is very small and feeble he may be fed small amounts every 2 or 3 hours by means of a special fine plastic tube passed down his throat into his stomach. The tube causes the baby no discomfort. Larger premature babies may be able to suck from a special bottle fitted with a soft teat, and babies over 2 kg, can usually feed from the breast. Small feeds are given frequently to reduce the risk of regurgitation during the first week or two of life and then the amount is increased gradually.
A strong bond develops between a mother and her baby even before birth and this takes the form of mothering which is so important after delivery, and even more important for the premature baby in an incubator. The mother sees her baby at the earliest opportunity and handles him as soon as his condition permits. The separation of the premature baby from his mother is unavoidable and although it may cause some heartache the normal physical and emotional relationships rapidly develop as soon as she is allowed to look after him.
Complications of the Premature Baby
The principal handicaps that the premature baby has to overcome at birth are respiratory difficulties and temperature control. He is also liable to infection, jaundice and anaemia.
Respiratory difficulty is due to the individual organs of the premature baby being immature in comparison to those of the normal full- term infant. Difficulty in respiration, causing shallow, irregular, rapid breathing may develop into a condition known as ‘respiratory distress syndrome’ to which, unfortunately, premature babies are particularly prone. Treatment of respiratory distress syndrome is supervised by the paediatrician. It is worth mentioning here that die production of surfactant (a substance that permits the lungs to remain open) is defective until about the 35 th week of gestation. However, it is apparent that giving steroids to the mother suspected of premature labour may enhance surfactant production thus helping the premature baby’s breathing. For this treatment to be effective, the steroids must have been given for 48 hours before the baby’s birth. Whilst this important observation and treatment is still under investigation, many obstetricians give steroid injections to their patients in early premature labour because they are already sufficiently convinced of the beneficial effect.
Temperature control of the premature baby is difficult and a relatively uniform body temperature is achieved by placing him in an incubator.
Infection. The premature baby is very susceptible to infections because his resistance is extremely poor. Breast-feeding plays an ‘important part in protecting the baby and, therefore, breast-milk is particularly beneficial to the small, feeble, premature baby. Everyone who handles the baby should have clean, washed hands. This has an enormous effect on lowering the incidence of infection in the new-born, and cannot be overemphasized.
Jaundice appearing in the premature baby at any time during the first week or two of life is fairly common. The baby is frequently examined so that he can be treated if the jaundice becomes too severe.
Anaemia. Iron deficiency anaemia may develop in premature babies or those of low birth weight. New-born babies, whatever their maturity, have reasonable iron reserves. However, the small baby grows more rapidly in proportion to his birth weight than does the large baby so that he exhausts his store of iron quite quickly and is liable to iron deficiency anaemia. To prevent this the premature baby is given iron by mouth from the age of 4 weeks. In the full-term infant an iron deficiency anaemia is best prevented by the introduction of mixed feeding with foods rich in iron at the age of 3 months.
Progress of the Premature Baby
Premature babies develop and progress normally and after a few weeks no one would know that they had been born prematurely. The length of time they are kept in an incubator varies according to their maturity and birth weight, and the baby is usually kept in hospital until he teaches 2.5 kg. Most premature baby units encourage mothers to participate in the daily care of their babies after they have been taken out of die incubator so that each mother is quite capable of looking after her baby when he leaves hospital.