Abstract 93

Aims-To identify antepartum predictors of Newborn Encephalopathy(NE) in term infants.

Methods- A population-based unmatched case control study in the metropolitan area of Western Australia from June 1993 to Sept 1995. Outcome measures - adjusted odds ratios.

Subjects- 164 term infants with moderate or severe NE; 400 randomly selected term controls.

Results- The birth prevalence of NE was 3.8/1000 term live births with a neonatal case fatality of 9.1%. Preconceptional risk factors of NE included the mother being unemployed (OR 3.60), an unskilled manual worker(OR 3.84), or a housewife (OR 2.48) or having a family history of seizures(OR 2.55), or neurological disease (OR 2.73). The risk of NE increased with increasing maternal age and decreased with increasing parity. Not having private health insurance (OR 3.46), and receiving infertility treatment (OR 4.43) were associated with increased risk. Pregnancy risk factors were maternal thyroid disease (OR 9.70), severe pre-eclampsia (OR 6.30), moderate or severe bleeding (OR 3.57), a clinically diagnosed viral illness (OR 2.97), not having drunk alcohol (OR 2.91), and having a placenta described as abnormal at delivery (OR 2.07). Intra-uterine growth retardation adjusted for gestational age had a significant association with NE, between the third and the tenth centile (OR 4.37) and below the third centile (OR 38.23).

Conclusions- The causes of newborn encephalopathy are heterogeneous and many start in the antepartum period. These findings challenge the view, particularly the medico-legal view that the origin of NE lie exclusively in the intrapartum period.