oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
The World Health Organization (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. 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.
It is not uncommon for babies to be both early and to have intrauterine growth restriction (IUGR), which adversely affects their prognosis. Quoting figures may be misleading as they will vary considerably amongst units; however, figures that are not atypical include:
- 90% survival if over 800 g.
- 50% survival if over 500 g.
- 80% survival in those born before 28 weeks of gestation.
These figures may also hide significant disability in survivors.
The baby who is also small for gestational age (SGA) 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 intrauterine growth restriction (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 SGA. 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 (SCBU) 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 few or no long-term problems but those who are very premature and who have a stormy start to life often suffer many and serious problems.
Long-term problems of premature babies
Morbidity is inversely related to gestational age; however, there is no gestational age (including term) that is wholly exempt. 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. 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 birthweight below 1.5 kg has peripheral or central hearing impairment, or both.
Infants who undergo early screening and treatment for retinopathy of prematurity (ROP) have improved long-term functional and structural outcomes compared with those who receive conventional screening and treatment. However, the increased survival of lower birthweight infants has increased the prevalence of aggressive, posterior ROP 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.
Childhood hospital admissions
Extremely low birthweight (birthweight 500-999 g) children have more hospital readmissions and other health problems in the early years after discharge than do normal birthweight (birthweight >2499 g) children. Respiratory illnesses, including lower respiratory infections, are the dominant cause for hospital readmission.
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:
- 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.
- 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 aged 7 and 8 who were born before 32 weeks and who were well enough to attend mainstream school. 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 co-ordination 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.
Intrauterine growth restriction (IUGR) may be very important in terms of early growth of the brain, leading to poor IQ and developmental skills. 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.
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.
A study of 18 and 19 year-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.
A study of preterm 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.
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). 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.
- Secondary - antenatal care is important and should be easily accessible to all women.
- Tertiary - interventions when complications arise, eg regionalised care, treatment with antenatal corticosteroids, tocolytic agents and antibiotics.
Supporting the parents
When a baby is in the Special Care Baby Unit (SCBU) it is a very emotional and traumatic time for both the parents. They should be encouraged to visit and stay with the baby as much as possible. Breast-feeding may be rather difficult but it should be encouraged. Breastmilk is the best food for any baby but especially premature babies. Mothers who are producing more than their own baby's 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. 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.
The success of improved survival in very premature infants has raised some serious ethical issues. It is now possible to save more, smaller and earlier babies. The difficult question is whether this is always in the best interest of the baby, their parents and society in general.
- Such babies have a very high incidence of both physical and behavioural problems. There may be blindness, deafness, mental handicap or attention deficit hyperactivity disorder (ADHD). The quality of life of the surviving child can be difficult to assess.
- The term bed blockers is usually used pejoratively of the elderly but tiny, very early babies spend a very long time in Special Care Baby Unit (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.
- Who could ever make the decision that the quality of life salvaged is not worthy of the effort and cost? 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 have fuelled a debate about the upper limit for termination of pregnancy.
Further reading & references
- Premature Babies UK; Home page
- BLISS; Information and support for parents
- Perinatal Management of Pregnant Women at the Threshold of Infant Viability (The Obstetric Perspective), Scientific Impact Paper No. 41, Royal College of Obstetricians and Gynaecologists (Feb 2014)
- Moser K, Macfarlane A, Chow YH, et al; Introducing new data on gestation-specific infant mortality among babies born in 2005 in England and Wales. Health Stat Q. 2007 Autumn;(35):13-27.
- Ip S, Glicken S, Kulig J, et al; Management of neonatal hyperbilirubinemia. Evid Rep Technol Assess (Summ). 2002 Nov;(65):1-5.
- Rennie JM, Sehgal A, De A, et al; Range of UK practice regarding thresholds for phototherapy and exchange transfusion in neonatal hyperbilirubinaemia. Arch Dis Child Fetal Neonatal Ed. 2009 Sep;94(5):F323-7. Epub 2008 Nov 10.
- Saigal S, Doyle LW; An overview of mortality and sequelae of preterm birth from infancy to adulthood. Lancet. 2008 Jan 19;371(9608):261-9.
- Hack M, Costello DW; Decrease in frequency of cerebral palsy in preterm infants. Lancet. 2007 Jan 6;369(9555):7-8.
- Jiang ZD, Brosi DM, Wilkinson AR; Hearing impairment in preterm very low birthweight babies detected at term by brainstem auditory evoked responses. Acta Paediatr. 2001 Dec;90(12):1411-5.
- Quiram PA, Capone A Jr; Current understanding and management of retinopathy of prematurity. Curr Opin Ophthalmol. 2007 May;18(3):228-34.
- Guideline for the screening and treatment of retinopathy of prematurity, Royal College of Ophthalmologists (2008)
- Allin M, Rooney M, Cuddy M, et al; Personality in young adults who are born preterm. Pediatrics. 2006 Feb;117(2):309-16.
- Doyle LW, Ford G, Davis N; Health and hospitalistions after discharge in extremely low birth weight infants. Semin Neonatol. 2003 Apr;8(2):137-45.
- Larroque B, Ancel PY, Marret S, et al; Neurodevelopmental disabilities and special care of 5-year-old children born before 33 weeks of gestation (the EPIPAGE study): a longitudinal cohort study. Lancet. 2008 Mar 8;371(9615):813-20.
- Marlow N, Wolke D, Bracewell MA, et al; Neurologic and developmental disability at six years of age after extremely preterm birth. N Engl J Med. 2005 Jan 6;352(1):9-19.
- Foulder-Hughes LA, Cooke RW; Motor, cognitive, and behavioural disorders in children born very preterm. Dev Med Child Neurol. 2003 Feb;45(2):97-103.
- Cooke RW; Are there critical periods for brain growth in children born preterm? Arch Dis Child Fetal Neonatal Ed. 2006 Jan;91(1):F17-20. Epub 2005 Oct 13.
- Nosarti C, Al-Asady MH, Frangou S, et al; Adolescents who were born very preterm have decreased brain volumes. Brain. 2002 Jul;125(Pt 7):1616-23.
- Gardner F, Johnson A, Yudkin P, et al; Behavioral and emotional adjustment of teenagers in mainstream school who were born before 29 weeks' gestation. Pediatrics. 2004 Sep;114(3):676-82.
- Cooke RW; Health, lifestyle, and quality of life for young adults born very preterm. Arch Dis Child. 2004 Mar;89(3):201-6.
- Iams JD, Romero R, Culhane JF, et al; Primary, secondary, and tertiary interventions to reduce the morbidity and mortality of preterm birth. Lancet. 2008 Jan 12;371(9607):164-75.
- Pregnancy and alcohol, Dept of Health, July 2008; DH Alcohol Publications
- Zupancic JA, Kirpalani H, Barrett J, et al; Characterising doctor-parent communication in counselling for impending preterm delivery. Arch Dis Child Fetal Neonatal Ed. 2002 Sep;87(2):F113-7.
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Dr Hayley Willacy
Dr Hayley Willacy