What is Asphyxia and when does it occur?

Asphyxia is said to occur when the oxygen supply to the baby (or part of the baby’s body) is reduced to critical levels. It follows the effect of two events:  where oxygen levels fall to very low levels (termed hypoxia) or where blood supply is interrupted (termed ischaemia). If asphyxia persists, then it can cause damage to critical organs.

Asphyxia can occur before birth, during birth, or (less commonly) due to major complications after birth leading to sudden collapse.

Who is affected and what are the risk factors?

Asphyxia at birth occurs in 1-2 per thousand births at full term, leading to a brain condition called encephalopathy (or hypoxic-ischaemic encephalopathy or HIE). It may be slightly more common during preterm birth but preterm babies often tolerate low oxygen levels somewhat better than babies born at or near term, and signs that the baby has been affected may be less common.
Asphyxia at birth is more common with maternal complications such as diabetes or hypertension.

What is the cause?

While in the womb, the baby receives oxygen from the mother’s blood through the placenta and the umbilical cord.

Asphyxia can occur when this oxygen transfer is disrupted, for example because

  • the umbilical cord becomes blocked or stretched,
  • the blood flow is reduced because of  low maternal blood pressure.
  • the placenta separates from the womb early (called placental abruption).

These serious complications are difficult to identify early or to stop.

After birth, if breathing or circulation are disturbed for long periods because of severe illness such as infection, similar events can occur.

How is it diagnosed?

Before birth, fetal monitoring of the heart rate is used to give early warning of asphyxia. The lack of oxygen can also be detected through blood tests: a blood sample showing too much acid in the blood can indicate impending problems leading to early delivery.  Samples of blood are frequently taken from the umbilical cord blood vessels at birth as a measure of what has happened.

After birth, babies who are suspected of asphyxia are examined carefully for signs of brain function, checking for the presence of altered function, which can be scored or graded to indicate severity.  In addition, the electroencephalogram (EEG) is often used to check on the level of brain electrical activity, or ultrasound is used to identify any major problems.  Later on, the healthcare team may suggest a magnetic resonance scan (MRI) to determine if there is evidence of brain injury.

Other organ systems may also be affected by asphyxia, but tend to recover usually without problems – The healthcare team will explain if any tests are needed to show this.

How is it managed?

The major treatment strategy is to ensure that oxygen is delivered to all tissues in the body by increasing the level of oxygen the child breathes, or by ensuring that the blood pressure is maintained. Sometimes, extra drugs are needed to do this.  

For babies who are delivered after 35 weeks, sometimes cooling the baby’s body temperature to 33 degrees (normal is 37 degrees) is used to prevent ongoing brain injury. A transfer to a specialist centre may be needed for this to be carried out.

© 2018 EFCNI - European Foundation for the Care of Newborn Infants
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