Premature Babies and their Problems

WHO defines prematurity as babies born before 37 weeks from the first day of the last menstrual period.

In England and Wales, in 2005, there were 11,657 infants born at less than 33 weeks of gestation, more than 90% of whom survived the immediate postpartum period.¹

There are really two different problems of small babies:

• One is prematurity that means being unready for the extra-uterine world.
• The other is small for dates (SFD) that represents intrauterine growth retardation (IUGR).

It is not uncommon for babies to be both early and to have suffered IUGR.

The frequency of preterm births is about 5-9% in many developed countries and around 12-13% in the USA. The rate of preterm birth has increased in many locations predominantly because of increasing preterm delivery of artificially conceived multiple pregnancies.²About 7% of babies in the UK weigh less than 2.5 kg at birth, rising to 10% in deprived areas such as Hackney.³

Simply labelling all babies born before 37 weeks as premature fails to illustrate the marked gradation in terms of severity of the problem with increasing prematurity:

• A baby born at 36 weeks will probably be a little slow to feed.
• A baby born before 33 weeks will have more serious problems including, possibly, immature lungs.
• Birth before 28 weeks causes very significant problems but the survival rate is quite remarkable.

Quoting figures may be misleading as they will vary considerably amongst units but figures that are not atypical include 90% survival if over 800g, 50% survival if over 500g and 80% survival before 28 weeks. These figures may also hide significant disability in survivors.

There are a number of risk factors for early delivery:

• Induction or caesarean section may have been undertaken because of serious adverse intrauterine conditions:
  • This may include fulminating pre-eclampsia or abruptio placentae.
  • The decision that has to be made is "Is the baby safer in or out?" This is a matter of balancing risks.
  • Caesarean delivery is not associated with either reduced mortality or neuro-disability at two years of age. It is advised therefore that the method of delivery of these infants should be based on obstetric or maternal indications rather than the perceived outcome of the baby.⁴
• Multiple pregnancy often leads to premature labour and this may be very early if multiple means more than twins.
• Other causes of a large uterus e.g. polyhydramnios.
• The classical story of cervical incompetence is one of progressively earlier labours in successive pregnancies with premature rupture of membranes and a painless early dilation of the cervix.
• Low socio-economic status, inadequate or absent antenatal care and poor maternal nutrition all predispose to premature labour. Low body mass index and periodontal disease are associated with premature delivery.²
• African-American and Afro-Caribbean women are two to three times more likely to deliver early than white women. However, not all of this difference can be explained by socioeconomic factors - gene/environment interactions are a factor.⁵
• Smoking and excessive alcohol consumption are also risk factors.
• Heroin withdrawal or too rapid reduction of methadone during the last trimester can induce premature labour:
  • Drug abusers must be encouraged to comply closely with their regimen and reduction of methadone should be slow in the last trimester.
  • Cocaine can also cause premature labour. It is a potent vasoconstrictor and this can have a devastating effect on placental function.
• Maternal age under 17 or over 35 years old.
• Bacterial vaginosis predisposes to premature labour.

The premature baby will look small and unprepared for this world. The baby who is also SFD may have little subcutaneous fat and the skin may appear wrinkled.

Because mortality rates have fallen, the focus for perinatal interventions is to reduce long-term morbidity, especially the prevention of brain injury and abnormal brain development. The premature baby faces a number of problems (these may be accentuated if there is also IUGR):

• Hypothermia is a great risk, especially if there is little subcutaneous fat. A premature baby is less able to shiver and to maintain homeostasis.
• Hypoglycaemia is also a risk, especially if SFD. There may also be hypocalcaemia. Both can cause convulsions that may produce long term brain damage.
• The more premature the baby, the greater the risk of respiratory distress syndrome. Steroids before delivery may reduce the risk but it is still very real. If the baby requires oxygen it must be monitored very carefully as if the levels are too high the premature baby is susceptible to retrolental fibroplasia and blindness.
• The premature baby is more susceptible to neonatal jaundice and to kernicterus at a lower level of bilirubin than a more mature baby.
• They are susceptible to infection and to necrotising enteritis.
• They are susceptible to intraventricular brain haemorrhage with serious long term effects.

All these are problems faced by the neonatologist in the Special Care Baby Unit but when the baby is eventually discharged from hospital and goes home with the family, that is not the end of problems. The baby who is just slightly premature will probably have little on no long term problems but those who are very premature and who have a stormy start to life often suffer many and serious problems.

When a baby is in SCBU it is a very emotional and traumatic time for both the parents, not just the mother. They should be encouraged to visit and stay with the baby as much as possible. Breastfeeding may be rather difficult but it should be encouraged.⁶ Breastmilk is the best food for any baby but especially premature babies. Mothers who are producing more than their own baby needs should be encouraged to donate to the local SCBU as it is always welcome.

The baby is attached to monitors and has tubes in and out of the body. It may not be possible to hold the baby or it may not be possible to do so for long. This should be encouraged as much as is compatible with the safety of the baby but bonding is much more difficult than with a normal, healthy, full term baby.

Whilst trying to keep a positive attitude, the parents must also come to terms with the fact that the baby could die. There may also be difficult decisions about switching off ventilators and the expected quality of life if the child survives. Communicating in these situations can be difficult and parents may have trouble taking in what they are told at such an emotional time.⁷ They may wish to discuss matters with the familiar face of their family doctor who is outside the hospital but who understands the issues involved.

Immunisations

Premature babies need to be protected by immunisations as much as any other baby and prematurity is not a contraindication to immunisation even if the immune system may be immature. The timing of immunisations is based on the child's chronological age from birth and not on the child's putative age based on maturity.⁸

Morbidity is inversely related to gestational age; however, there is no gestational age (including term) that is wholly exempt.⁹ Severe problems such as cerebral palsy, blindness and deafness may affect as many as 10 to 15% of significantly premature babies. There is some evidence that the incidence of cerebral palsy is falling in premature babies born between 28-31 weeks.¹⁰
Figures about outcomes for premature babies have to be interpreted with a degree of circumspection to be sure that like is being compared with like:

• Percentages should be taken with caution.
• Different studies use different criteria for the degree of prematurity for inclusion.
• There is a gradation of risk.
• Being both premature and small for dates would seem to add further to the risk.

Sight and hearing

About 1 in 4 babies with birth weight below 1.5 kg has peripheral or central hearing impairment or both.¹¹

Infants who undergo early screening and treatment for retinopathy of prematurity have improved long-term functional and structural outcomes compared with those who receive conventional screening and treatment.¹² However, the increased survival of lower birth weight infants has increased the prevalence of aggressive, posterior retinopathy of prematurity that may be unresponsive to conventional treatment.
In a multicentre study 66% of babies under 1.25 kg developed ROP, but only 6% required treatment.¹³

Follow up to school

Cognitive and neuromotor impairments at 5 years of age increase with decreasing gestational age. Many of these children need a high level of specialised care:¹⁴

• About half of infants born at 24–28 weeks of gestation have a disability at 5 years, similar to the proportion observed in the UK-based EPICure study.¹⁵
• In the infants born later (29–32 weeks' gestation), about a third have a disability at 5 years.

Behavioural and psychomotor problems

A study from Liverpool has looked at children of 7 and 8 who were born before 32 weeks and who were well enough to attend mainstream school.¹⁶ They were compared with full-term children of similar age in their class at school:

• Disabilities can be subtle and numerous and so a range of tests was used.
• The preterm children had a higher incidence of motor impairment and this affected how well they did at school even when their intelligence was normal.
• Over 30% had developmental coordination disorder (DCD) compared with 6% of classmates.
• The preterm children were significantly more likely be overactive, easily distractible, impulsive, disorganised and lacking in persistence. They also tended to overestimate their ability.
• Attention deficit hyperactivity disorder (ADHD) was found in 8.9% of the preterm children and 2% of controls.
• The children who had been the most premature were not necessarily those with the lowest scores.

Although major disabilities have been reduced, the levels of disability tested in this study did not seem lower than those found in children born 10 or 20 years earlier, despite improvements in care of the newborn.

Brain development

IUGR may be very important in terms of early growth of the brain leading to poor IQ and developmental skills.¹⁷ Individuals who were born before 33 weeks gestation continue to show noticeable decrements in brain volumes and striking increases in lateral ventricular volume into adolescence.¹⁸

Emotional development - teens and beyond

A study of teenagers in mainstream schools who were born before 29 weeks gestation showed that compared with mainstream classmates, they have higher levels of parent and teacher reported emotional, attentional, and peer problems well into their teens. Despite these problems, they do not show signs of more serious conduct disorders, delinquency, drug use, or depression.¹⁹

A study of 18 and 19 years olds who were born before 33 weeks gestation showed that they had different personalities from controls with increased neuroticism and decreased extraversion scores. This was more marked in females than males.¹³

A study of pre-term children who had reached 19 to 22 years of age showed that they were, on average, shorter than their contemporaries, more likely to use prescription medicines and less likely to have attended higher education.²⁰

Interventions to reduce the morbidity and mortality of preterm birth can be primary (directed to all women), secondary (aimed at eliminating or reducing existing risk), or tertiary (intended to improve outcomes for preterm infants).²¹ Most efforts so far have been tertiary interventions.

• Primary - Problems of social deprivation, poor maternal nutrition and substance abuse must all be addressed. Smoking should cease and, as explained in the article on fetal alcohol syndrome, alcohol consumption should be avoided as there may be no safe lower limit.²²
• Secondary - Antenatal care is important and should be easily accessible to all women.
• Tertiary - Interventions when complications arise e.g. regionalised care, treatment with antenatal corticosteroids, tocolytic agents and antibiotics.

The success of improved survival in very premature infants has raised some serious ethical issues. It is now possible to save more and more smaller and earlier babies but is this a good thing?

• Such babies have a very high incidence of both physical and behavioural problems. This may be blindness, deafness, mental handicap or ADHD. Is the quality of life really worth the enormous input?
• The term bed blockers is usually used pejoratively of the elderly but tiny, very early babies spend a very long time in SCBU cots that are in short supply. They may be depriving other babies of facilities from which they would extract greater benefit. The cost of SCBU care is also very high and finance is not a limitless resource.
• However, premature babies can become extremely productive, as shown by the list of famous premature babies on the premature babies uk website. It includes Albert Einstein, Isaac Newton and Charles Darwin.
• When should neonatologists decide that the quality of life that they salvage is not worthy of the effort? When would it be better to let tiny babies die? This is a very difficult question that will raise much passion and prejudice but it is an extremely important issue that does require sober assessment.
• The high survival rates that are achieved by some units for very premature babies has fuelled a debate about the upper limit for termination of pregnancy.