Physiological Maturity of Preterm Infants 2500 words

Contrast the physiological maturity of a preterm 35 week gestation infant and that of a term 40 week gestation infant. Identify the physiological and developmental problems that can arise as a result of the differences in function.

A full term baby is approximately 20 inches or 52 cm in length and 7 lbs 7 oz or 3.5 kilograms in weight, boys being slightly larger on average than girls. Apart from obvious differences such as smaller weight and size an infant of only 35 weeks gestation will have other differences that may have some long term effects on his health. Someone once said that every day longer in the womb will mean two less days in hospital. However it is sometimes difficult to separate problems caused by lack of maturity to those caused by the reason for the early delivery e.g. spontaneous rupture of membranes in an otherwise normal pregnancy opens up the infant to greater risks of infection. Also the infants immune system is not yet fully developed, so he is less able to fight disease and is consequentially at higher risk from diseases such as that caused by the Respiratory Syncytial Virus or RSV, hence the increased frequency of conditions such as pneumonia in these children.

One of the factors to be considered is the maturity of his lungs compared with that of the full term baby. A recent report by Marvin Wang ( Pediatrics, August,2004) came to the conclusion that near term infants had significantly more problems than the full term children. The factors involved were several, but included such things as immature lung development and consequent respiratory distress , immaturity of the central nervous system, temperature instability, jaundice, risk of hypoglycaemia, apnoea and bradycardia and a weakness in the blood vessels of the skull that make the child more susceptible to brain haemorrhage. The child born at this stage is about 87% ready to be born, but in many cases this just isn’t quite a high enough percentage. Dr Wang and his colleagues came to the conclusion that near-term infants represented an as yet unrecognised neo-natal group at risk when the number of medical interventions necessary were measured.

Infants born at this stage , though falling below the average weight of a full term child, may still fall within some of the norms for that stage. He will appear normal in other ways – his nails will reach to the end of his fingers and toes, and he may have plenty of hair. Also his irises will dilate and shrink according to light levels and he can open his eyes at will.

Before birth the heart has a hole in its centre through which blood is shunted from side to side because the lungs are not in use. In the majority of cases this opening closes within hours of birth. It may be slower to do so in the pre-term infant and this will mean less blood is circulated to the lungs and oxygen levels will be depleted.

He will have less body fat than the full term child which will contribute to his lack of ability to maintain his body temperature at an adequate level.

Another factor is the size of the infant’s stomach. This is one of the last parts of a foetus to grow and so the stomach may be considerably smaller than that of a full term infant.

Immaturity of the infant’s central nervous system may result in low muscle tone and lack of respiratory effort and consequent problems with oxygen levels. This can also make a difference with the ability to suck.

It may be that this was a rapid labour due to the relatively small size of the foetus. This has its own dangers in that the skull may undergo quite fast compression and decompression, which could result in intracranial trauma.

Describe the nursing care management (with rationales) of a preterm infant born at 35 weeks gestation ( normal pregnancy prior to delivery, weight on 50th percentile for gestation.

The differences between nursing infants at this stage of gestation and those at full term are concerned with physiological differences between the two states as outlined above.

Gabriel Escobar, in his report regarding short term outcomes for these children, notes that

infants born at this stage make up about 7% of live births and, according to Escobar, 58.3 % of premature infants born in the United States. He noted an increased risk of re-hospitalization and also increased mortality rates, 6.9 per 1000 as opposed to 2.5 at full term. Whether the outcome is merely re-hospitalization, or something worse, the families involved would need extra support. They will need someone to listen to their fears and hopes and also information that can help them cope with their situation.

Children born at this stage may have Apgar scores ( measurements of such things as heart rate, reflexes, colour, respiration and muscle tone) within normal limits and so there there is a tendency to treat them just like full term infants.However these children are five times more likely to need ventilation as more mature infants. Acute respiratory distress is the most common problem seen in late-preterm babies. About 8% require extra oxygen support for an hour or more This is 3 times the number in infants just a week or so further on in maturity. The nurse needs to be aware of this when such a birth is imminent and make suitable preparations and also needs to be aware of the possible dangers of too high concentrations of oxygen such as retinopathy. Intubation may be required, so a pediatrician should be at hand. Even among infants who progress to respiratory failure, but do not have any major congenital abnormalities the mortality rate is higher than in those just a week more mature.. The administration of exogenous surfactant is almost routine where there is a possibility of respiratory distress occurring, and for the duration of the administration time, one to one nursing is recommended and the doctor should remain present for 30 minutes after intubation. Blood gases will need to be measured before and after administration. If a cannula is left in place so that blood tests can be more easily carried out the parents need to have this explained to them and also reassured that it is not painful for their child. Although an infant may appear quite pale, or even slightly blue at birth and soon after, its blood oxygen levels should soon give it a healthy pink glow. Nurses need to be able to distinguish between this and the blue tinge that will develop in an infant short of oxygen.

If oxygen is needed for a longer period it may prove difficult to feed an infant by bottle or breast. Babies tend to breath through their mouths and so may have difficulty in maintaining suction and in coordinating sucking and swallowing. They need more sleep and so are less likely to be awake enough to take in sufficient food and fluid. This situation could quickly develop into hypoglycemia and dehydration. Also lack of maturity of the central nervous system may mean that sucking action is weaker than the norm and the child may well be getting less than the normal 3 oz or so that a more mature infant will take at each feed in the first day or two of life. Care should be taken that they do not become dehydrated. The nurse can easily check for this by noting whether or not the fontenelles are depressed or there is any tenting of the skin – both signs of dehydration. Tube feeding will be necessary in these cases. If the mother wishes to breast feed milk can be expressed using a vacuum pump and given to the child. However as the building of the parent /child bond is so important it is best if the mother can feed the child herself where this is possible.

Because these infants can look and appear very similar to those born at full term there can be a false sense of security. The conclusions of various studies is that they do need extra care and attention. Nurses need to come up with a strategy that will mark out these infants so that their needs can be better assessed and met. For instance the lack of body fat means that they should be kept a little warmer than is normal or their temperature may drop. The slightly smaller stomach for instance will mean that they will need to be fed more frequently with smaller feeds than then more mature birthmates. Also it may be necessary to burp the child several times during a feed. Both mothers and staff need to be aware of this and of the fact that feeds should not normally last more than about 30 minutes or both mother and child will become exhausted. Careful note should be made of weights and, if breast feeding, weighing before and after feeds once a day will ensure that the child is fed adequately. It may be that a mother wishes to breast feed , but because the child was born pre-term she may not have sufficient milk at first, or the mother may be more nervous than usual. She will need to be reassured that this is normal, and that if she persists in putting the baby to the breast regularly the milk will eventually come in fully. In the mean time feeds can be supplemented. Mothers will need reassurance that this does not mean that they are failing in any way, but that this is simply due to the child’s relative immaturity. If feeding is required as often as two hourly this will mean that a mother would not get sufficient rest, so nurses could take over some of the feeds with bottled formula milk. The Academy of Breastfeeding Medicine states that the advantages of being breast fed for pre-term infants are even greater than those for full term ones. They suggest that a protocol be devised that will minimize problems that both mother and child may have, both in hospital and after returning home. A feeding plan should be drawn up as this will minimize the risk of a mother being given conflicting advice by various professionals. Someone specializing in lactation, especially in the pre-term infant, should be on hand and the mother needs to know that she will receive help and support as necessary. For instance a mother’s body heat may make her child sleepy so that he falls asleep rather than feeds. Holding him a little distant from the body, especially easy if he is being bottle fed, may be all it needs to overcome this difficulty.

The immaturity of the liver means that these infants may develop more than the usual amount of jaundice associated with the transition from foetal to adult haemoglobin. If this is allowed to develop into kernicterus then permanent neurological damage can be done including deafness and blindness. Jaundice needs to be monitored in a consistent way so that any excessive rise can be noted . This requires proper measurement , not just judging by a quick glance as normal skin tones vary considerably. It can be noted by pressing gently on the baby’s forehead in the first instance and watching as the colour returns. Later it will travel downwards to other parts of the body. There are sets of colour charts that can be used to compare a child’s skin colour quickly and increase in jaundice levels noted. These are easy to use an d take account of differing normal skin tones by measuring differences in that particular child. If in any doubt then blood bilirubin levels should be measured. Direct and indirect bilirubin levels – bilirubin can be bound with other substances by the liver so that it can be excreted (direct), or may be circulating in the blood circulation (indirect) together with red blood cell counts and testing for rhesus incompatibility using Coomb’s test.. Jaundice more likely to persist if the baby is getting insufficient fluids due to poor sucking reflex or lack of breast milk. It may be however that it is the jaundice that is causing lethargy and so poor feeding. Poor sucking can also be a sign of infection, perhaps that associated with premature rupture of membranes so nurses need to be aware not just of the child’s records, but the records of the pregnancy, especially immediate prior to delivery. Light therapy is commonly used to treat mild infantile jaundice, but it must be ensured that the infant’s eyes are protected form the light and that the child is moved from time to time so that all areas of the skin can be reached by the light. Temperature checks should be made in order to ensure that the child is not overheating. Jaundice that appears after about the third day is probably due to infection, so it is important to establish when it begins or if it was present at birth or soon afterwards.

Temperature needs to be consistently measured and the child kept in a warm environment until his body is stable enough to maintain a normal temperature.

Bradycardia, i.e. a pulse rate of less than 90 beats per minute in infants, can be benign or can be life threatening and is one of the possible problems mentioned and this again needs to be checked consistently, and the cause ascertained and possible treatment instigated.

If delivery was rapid there is a possibility of tearing of blood vessels near to the ventricles of the brain. This can be due to variations in blood pressure and these can also come about because of the use of a ventilator. Nurses need to be aware of this so that they can look for possible symptoms such as swelling of the fontanelles and even seizures and hemiplegia. Sometimes the symptoms are more subtle such as general failure to thrive.

All of these factors mean that infants born at 35-36 weeks may need more attention than has previously been realized. Their needs should be taken into account when planning work schedules and acquiring equipment. In August 2004 the B.B.C. reported results from a team at Massachusetts General Hospital who found that conditions such as jaundice and hypoglycaemia are much more common in infants at born at 35 -36 than in those of only a weeks more maturity. The latter was three times as common and nearly half were jaundiced. Some needs of these children may not be as obvious as those of the severely immature infant, but are real nevertheless. There is a tendency for hospital stay post-delivery to get ever shorter.

A number of factors are involved here, not least financial, but such a short stay means that there is barely time for the mother to get used to her new state, let alone be taught adequately about how to look after her near-term infant. Nurses need to be aware of this situation and ensure to the best of their abilities that parents receive the correct advice or have it available to them. Without giving cause for concern she should be told what help is available and the health authority needs to ensure that adequate support is provided, both in the case of healthy children and those with problems.

Electronic sources

B.B.C. August 2004 Warning of near-term birth risk accessed 26th July 2007

Escobar,G. et al , Short term Outcomes of Infants Born at 35 and 36 Weeks Gestation. 2006 accessed 26th July 2007 The Academy for Breast Feeding Medicine, Breast feeding the Near- Term Infant accessed 26th July 2007

The Hospital for Sick children, July 2007 Intraventricular haemorrage accessed 26th July 2007

Wang,M. et al, Clinical Outcomes of Near Term Infants

PEDIATRICS Vol. 114 No. 2 August 2004, pp. 372-376 accessed 26th July 2007