Prematurity is defined as birth before 37 weeks gestation. The more premature the baby, the worse the outcomes. The prognosis improves with each additional week of gestation. Resuscitation in babies under 500 grams or 24 weeks gestation should be carefully considered.
The World Health Organisation (WHO) classify prematurity as:
- Under 28 weeks: extreme preterm
- 28 – 32 weeks: very preterm
- 32 – 37 weeks: moderate to late preterm
Risk Factors
- Social deprivation
- Smoking, alcohol or drug use
- Overweight or underweight mother
- Maternal co-morbidities (e.g., diabetes or hypertension)
- Multiple pregnancy (including twins)
- Personal or family history of prematurity
Management Before Birth
In women with a history of preterm birth or an ultrasound demonstrating a cervical length of 25mm or less before 24 weeks gestation, there are two options for trying to delay birth:
- Prophylactic vaginal progesterone (putting a progesterone suppository in the vagina to discourage labour)
- Prophylactic cervical cerclage (placing a suture in the cervix to hold it closed)
Where preterm labour is suspected or confirmed, there are several options for improving the outcomes:
- Tocolysis with nifedipine (a calcium channel blocker that suppresses labour)
- Maternal corticosteroids are offered before 35 weeks to reduce neonatal respiratory distress and mortality
- IV magnesium sulphate is offered before 34 weeks for neuroprotection (to reduce the risk of cerebral palsy)
- Delayed cord clamping increases the circulating blood volume and haemoglobin in the baby
Issues In Early Life
- Respiratory distress syndrome due to immature lungs
- Hypothermia due to difficulty regulating body temperature
- Hypoglycaemia due to limited glycogen stores
- Poor feeding due to immature reflexes
- Apnoea and bradycardia due to autonomic nervous system immaturity
- Neonatal jaundice due to liver immaturity
- Intraventricular haemorrhage (bleeding in the ventricles of the brain)
- Retinopathy of prematurity (abnormal blood vessel development in the retina stimulated by hypoxia)
- Necrotising enterocolitis (inflammation and necrosis of the bowel)
- Infections due to an immature immune system
Long Term Effects
- Bronchopulmonary dysplasia (long-term lung dysfunction)
- Neurodevelopmental issues (e.g., learning disability and behavioural difficulties)
- Susceptibility to infections, particularly respiratory tract infections
- Visual impairment
- Hearing impairment
- Cerebral palsy
Last updated May 2025
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