The fetus at the tipping point: modifying the outcome of fetal asphyxia

Abstract

Brain injury around birth is associated with nearly half of all cases of cerebral palsy. Although brain injury is multifactorial, particularly after preterm birth, acute hypoxia-ischaemia is a major contributor to injury. It is now well established that the severity of injury after hypoxia-ischaemia is determined by a dynamic balance between injurious and protective processes. In addition, mothers who are at risk of premature delivery have high rates of diabetes and antepartum infection/inflammation and are almost universally given treatments such as antenatal glucocorticoids and magnesium sulphate to reduce the risk of death and complications after preterm birth. We review evidence that these common factors affect responses to fetal asphyxia, often in unexpected ways. For example, glucocorticoid exposure dramatically increases delayed cell loss after acute hypoxia-ischaemia, largely through secondary hyperglycaemia. This critical new information is important to understand the effects of clinical treatments of women whose fetuses are at risk of perinatal asphyxia.

Keywords: brain injury; fetus; hypoxia.

Figure 1. Schematic diagram illustrating the phases of evolving hypoxic–ischaemic (HI) brain injury

Examples of when endogenous neuroprotective factors are released are shown at the top. Examples of factors which modify the perinatal adaptation to HI are shown below. Factors that can increase neural injury or risk of neurodevelopmental impairment are denoted by up arrows, while factors associated with evidence for decreased injury and impairment are denoted by down arrows. SNS (sympathetic nervous system), insulin‐like growth factor 1 (IGF‐1), electroencephalographic activity (EEG).