THE cerebral palsies are a heterogeneous group of non-progressive developmental disorders affecting movement and posture.
Their prevalence of 2–2.5 per 1000 births has changed little since cerebral palsy registers began 57 years ago, despite a sixfold increase in caesarean birth. They are heterogeneous in clinical type, in brain imaging pathology, in their association with other neurological disability and in their genetic and epidemiological associations.
In a recent paper published in Obstetrics and Gynecology researchers describe a case–control study of 494 singleton infants with cerebral palsy born after 35 weeks gestation, included on the WA Register of Developmental Anomalies, and 508 matched controls. They found that birth defects (42.3%) and fetal growth restriction (16.5%) contributed more to cerebral palsy than potentially asphyxial birth events (8.5%) and inflammation (4.8%).
These data confirm and extend the findings of other epidemiological studies and particularly underline the antenatal origins of most of the cerebral palsies.
The strong association of cerebral palsy with birth defects suggests genetic and epigenetic pathways to many of these cases. Very preterm delivery can initiate another common pathway via intraventricular haemorrhage, ventriculomegaly and white matter damage.
Next generation genetic sequencing technologies are allowing other pathways to cerebral palsy to be explored. Genetic susceptibility and environmental triggers may combine during pregnancy to stimulate networks and pathways to cerebral palsy that in the future may be amenable to intervention.
Fetal growth restriction, a major risk factor for cerebral palsy, can be missed if a customised birthweight for gestational age chart is not used that includes the sex and ethnic group of the newborn, and maternal height and weight (www.gestation.net). The ponderal index can further assess asymmetrical fetal growth restriction, which is a sign of chronic fetal stress and may reflect existing pathology contributing to pathways leading to intrauterine neuropathology.
Growth-restricted fetuses may not tolerate labour well and acute-on-chronic hypoxia may arise, making the timing of the neuropathology difficult to ascertain.
Giving magnesium sulfate to women before very preterm delivery slightly reduces the risk of cerebral palsy and in selected cases of presumed intrapartum hypoxia head cooling may also reduce risk but these interventions have yet to impact much on the overall prevalence of cerebral palsy.
In particular, both elective caesarean delivery before labour and emergency caesarean delivery during labour have not reduced the risk of cerebral palsy as demonstrated in our systematic review and meta-analysis of observational studies, published last month in Obstetrics and Gynecology.
Thus there are no epidemiological data to support medicolegal assumptions that earlier caesarean delivery would have prevented a cerebral palsy outcome.
A very small number of cases of cerebral palsy could result purely from a severe acute asphyxial event in labour in a previously uncompromised healthy fetus, and there are published consensus criteria to help define these uncommon cases, which usually are associated with hypoxic sentinel events such as cord prolapse, uterine rupture and antepartum haemorrhage. In such cases speedy delivery is attempted and the available staff and facilities will determine the decision-to-delivery interval.
However, these intervals can garner criticism from armchair plaintiff medicolegal witnesses. Placental histology and arterial cord gases should be sought in all deliveries requiring obstetric or neonatal intervention to better inform and to minimise surmise.
Fear of cerebral palsy litigation and the high false-positive rate of electronic fetal monitoring contribute to the high rates (33%) of caesarean deliveries in Australia, the UK and the US.
An audit of maternity services in England last month decried the fact that 20% of expenditure in maternity services was for “negligence cover” and the main quantum was in cerebral palsy litigation.
Australian insurance agencies annually pay more than $200 million in mostly out-of-court settlements for cerebral palsy outcomes. Up to 70% of litigation costs are spent on the legal process.
The National Disability Insurance Scheme will not cover the main claim of litigants for “heads of damages”, eg, loss of income and quality of life, and thus cerebral palsy litigation is likely to continue to the detriment of maternity services. In comparison, funding for cerebral palsy research is a tiny fraction of these payments.
It is time Australia has a “no-fault” pension scheme for all cases of cerebral palsy, as it would be cheaper, much more equitable and it would exclude lawyers and expert witnesses.
Emeritus Professor Alastair MacLennan is the head of the Australian Collaborative Cerebral Palsy Research Group, Robinson Institute, Discipline of Paediatrics & Reproductive Health, The University of Adelaide.