Premature babies and their problems

What is a premature baby?

The World Health Organization (WHO) defines prematurity as babies born before 37 weeks from the first day of the last menstrual period.

How common are premature babies?

Worldwide, it is estimated that 9.9% of all infants were born preterm in 2020, accounting for approximately 13.9 million premature babies and 1 million neonatal deaths.¹²

In England and Wales in 2022, 7.9% of all babies were born before 37 weeks, with the rates highest in the North West and lowest in the South West. This was a slight increase from the previous year. Approximately 48,000 infants were born at less than 37 weeks of gestation with 7,500 born at less than 33 weeks and 2,800 born at less than 28 weeks.³

Globally, there has been no significant change to the numbers of babies being born prematurely over the last decade. Southern Asia and sub-Saharan Africa have the highest proportion of premature births. They also have the highest risk of neonatal deaths.

It is not uncommon for babies to be both early and to have intrauterine growth restriction (IUGR), which adversely affects their prognosis. IUGR occurs where the baby's growth slows down or becomes static while still in the uterus. It is part of a wider group referred to as small for gestational age (SGA) fetuses where the fetus is smaller than expected for the gestational age. SGA includes fetuses which are constitutionally small and those whose growth has been restricted.

Preterm survival at the earliest gestational ages has improved dramatically in high-income countries, where the limit of viability has extended to 22-23 weeks of gestation. In the UK, 0.14% of live births are at less than 24 weeks of gestation.⁴ However, survival at these gestational ages in low- and middle-income countries is much less common, despite 80% of births worldwide now taking place in medical facilities.¹ Quoting survival figures may be misleading as they will vary considerably amongst units and with gestational age, ethnicity, sociodemographic and genetic factors.⁵In the UK, in 2022, in babies born at less than 32 weeks' gestation who were admitted to neonatal units, 93.5% survived to be discharged to home.

Improving survival at lower gestations and weight makes it challenging for health professionals and parents to choose the right course of action for babies born at limits of viability. The Royal College of Obstetricians and Gynaecologists (RCOG) has published guidance to help with this difficult issue. Their guidance recommends that extremely premature infants (those born at less than 27 weeks' gestation) be categorised into moderate (less than 50% change of dying or surviving with severe impairments), high (50-90% chance of dying or surviving with severe impairments) and extremely high risk (greater than 90% chance of dying or surviving with severe impairments). These groups are no longer purely based on birthweight but include other factors, although gestation and IUGR remain important. Guidance advises on whether babies should be cared for on an active or palliative pathway.⁶

Immediate complications for premature babies

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 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 reduce the risk but do not eliminate it. If the baby requires oxygen, this must be monitored very carefully as premature babies are susceptible to retrolental fibroplasia and blindness with high oxygen levels.

• The premature baby is more susceptible to neonatal jaundice and to kernicterus at a lower level of bilirubin than a more mature baby.⁷

• They are susceptible to infection and to necrotising enteritis.

• They are susceptible to intraventricular brain haemorrhage with serious long-term effects.

Long-term problems of premature babies

Premature babies often have ongoing problems which continue into later life. Survival to discharge from a neonatal unit does not mean an uncomplicated developmental path from then on.

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.⁸

In the infants born between 29 and 32 weeks of gestation, about a third have a disability at 5 years.

Morbidity is inversely related to gestational age; however, there is no gestational age that is wholly exempt. Data from EPICure studies confirm that prevalence of neurodevelopmental impairment was significantly associated with the length of gestation, with greater impairment as length of gestation decreased (45% at 22-23 weeks, 30% at 24 weeks, 25% at 25 weeks and 20% at 26 weeks).⁹ Cerebral palsy was present in 14% of the survivors from this group. There is some evidence that the incidence of cerebral palsy is falling in premature babies born between 28-31 weeks¹⁰ although this reduction appears to have stalled from 2010, and the prevalence in children born before 27 weeks appears to be stable.¹¹

A large French study followed up 5,567 neonates born alive in 2011 at 22-34 completed weeks of gestation, with 4,199 survivors at 2 years (corrected age) included in follow-up. The rates of survival and survival without severe or moderate neuromotor or sensory disabilities increased during a period of two decades, but these children remained at high risk of developmental delay. There was a statistically important decrease in the rate of cerebral palsy but the risk of developmental delay was high, even in children born moderately preterm.¹²

Other than the immediate or short-term complications mentioned above, premature babies have been shown to have increased risks of:¹³

• Respiratory issues

  • Bronchopulmonary dysplasia, which usually improves gradually over the first few years but can lead to subtly reduced lung function even in older children and adults.¹⁴

  • Recurrent episodes of acute lower respiratory tract infections, such as bronchiolitis, leading to increased rates of repeated hospitalisations.

• Cardiovascular issues:

  • Heart failure.

  • Ischaemic heart disease.

  • Hypertension.

• Gastrointestinal issues:

  • Short bowel syndrome.¹⁵

• Metabolic issues:

  • Obesity.

  • Lipid disorders.

  • Insulin resistance and type 2 diabetes.

  • Metabolic syndrome.

• Renal issues:

  • Chronic kidney disease.

  • Reduced nephron numbers.

• Neurological and cognitive factors:

  • Cerebral palsy.

  • Motor delay (both fine and gross).

  • Cognitive impairment with lower IQ scores and lower academic performance.

• Mental health issues and neurodiversity:

  • Anxiety and depression.

  • ADHD.

  • ASD.

  • Different personality styles.¹⁶

It is important to recognise that many premature infants will have none or few of these complications but that, at a population level, there are increased risks. Breastfeeding has been shown to reduce some of the risks significantly.¹³

Specific long-term complications of prematurity

Cerebral palsy¹⁷

Children born preterm are at increased risk of cerebral palsy. The prevalence increases with decreasing gestational age. Independent risk factors include:

• Grade 3 or 4 intraventricular haemorrhage.

• Cystic periventricular leukomalacia.

• Neonatal sepsis.

• Bronchopulmonary dysplasia for which mechanical ventilation was still needed at 36 weeks' postmenstrual age.

• Antenatal steroids not given.

• Postnatal steroids given to babies born before 32+0 weeks of gestation.

Sight and hearing problems

There is an increased risk of hearing impairment in children born prematurely. This risk increases with decreasing gestational age. Studies have suggested that the incidence of hearing impairment is 20-30 times that of term infants,¹⁸ occurring in over 10% of those born extremely prematurely and in between 3 and 5% of those born between 25 and 32 weeks of gestation (compared with 0.2% of term infants).¹⁹Both improvements and deteriorations in hearing have been shown over the first few years of life in children who were born prematurely.¹⁸

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.²⁰ However, the increased survival of lower birth-weight infants has increased the prevalence of aggressive, posterior ROP that may be unresponsive to conventional treatment. Incidence varies between 12% and 36% in studies. ²¹

Behavioural and psychomotor problems

Children born prematurely have been shown to have reduced scores in motor skills, behaviour, reading, mathematics and spelling at primary school and these disabilities continue into secondary school with the exception of mathematics.²²

ADHD is seen twice as often in children born prematurely.²²

In children born extremely prematurely and of very low birth weight, studies looking at children between the ages of 6 and 36 months suggested that 64% of children showed stably normal cognitive function, 4.6% remained persistently delayed and 31.4% deteriorated over this time. Deterioration was linked to lower birthweights, retinopathy of prematurity and lower parental socio-economic status. Motor outcomes followed a similar pattern.²³

Parent-delivered motor interventions have been shown to have more impact than any other interventions on both cognitive and motor scores in the short term, and possibly the long term.²⁴

Emotional development - teens and beyond

Many previous studies have shown increased rates of problems with emotional regulation, attention and peer relationships in school-age children who were born prematurely. Various studies have shown increased risks of depression and anxiety (particularly in girls), reduced educational achievements and increased use of prescription drugs.

More recent studies have recognised the increased risks of neurodiversity in children born prematurely, with one study suggesting that autism was 3.3 times more likely in people born prematurely than those born at term, with 20% being affected.²⁵There appears to be a significant impact of the degree of prematurity with 22.6% of those born at 25 weeks and 6% of those born at 31 weeks diagnosed with autism in another study.²⁶

This increased recognition and understanding of neurodiversity probably accounts for the previous studies' findings and allows for improved provision within schools for children who were born prematurely.

Developmental follow-up¹⁷

The National Institute for Health and Care Excellence (NICE) has published recommendations for the follow-up of babies born prematurely. In addition to identifying the types of problems and the likelihood of them being present, the guideline also suggests rationales for follow-up.

Enhanced surveillance by a developmental team up to 2 years (corrected age) is suggested for children born preterm who are at increased risk of problems:

• Have a developmental problem or disorder.

• Increased risk of developmental problems or disorders, based on the following criteria:

  • Born before 30+0 weeks of gestation.

  • Born between 30+0 and 36+6 weeks of gestation and one or more of the following risk factors:

    • Brain lesion on neuroimaging, likely to be associated with developmental problems or disorders (for example, grade 3 or 4 intraventricular haemorrhage or cystic periventricular leukomalacia).

    • Grade 2 or 3 hypoxic ischaemic encephalopathy in the neonatal period.

    • Neonatal bacterial meningitis.

    • Herpes simplex encephalitis in the neonatal period.

NICE recommends considering enhanced developmental support and surveillance by a multidisciplinary team up to 2 years (corrected age) for children born preterm who do not meet the above criteria but are suspected of being at increased risk of developmental problems or disorders.

NICE also recommends a face-to-face developmental assessment at 4 years (uncorrected age) for all children born before 28+0 weeks of gestation.

Prevention

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).²⁷ Most efforts so far have been tertiary interventions.

• Primary - problems of social deprivation, poor maternal nutrition and substance abuse should be addressed. Smoking should cease and alcohol consumption should be avoided, as there may be no safe lower limit (fetal alcohol syndrome).

• 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. Progesterone treatment for women at risk of preterm labour, to prevent preterm birth, has been recognised as the most useful preventative intervention during pregnancy.²⁸²⁹

Parental support

It is a very emotional and traumatic time for any parent when their baby is in the neonatal unit. They should be encouraged to visit and stay with the baby as much as possible. Breastfeeding should be encouraged where possible and use of donor breastmilk is recommended where not possible.

Bonding is often more difficult than with a normal, healthy, full-term baby, but staff will be able to encourage parents to touch and hold their baby as much as is possible.

There may also be difficult discussions about the longer-term implications and about active vs palliative management.⁶ Communicating in these situations can be difficult and parents may have trouble taking in what they are told at such an emotional time.³⁰

Parents whose children require neonatal care are eligible for additional paid parental leave.