The role of antepartum and intrapartum factors in the etiology of neonatal encephalopathy (NE) in 164 term infants was investigated in a Western Australian case-control study, with 400 randomly selected controls. The prevalence of NE was 3.8/1000 term live births, with a 9.1% case fatality. The features of NE included seizures, abnormal tone, apneas, feeding difficulties, abnormal consciousness, and ventilatory support. Independent risk factors before conception and in the antepartum period included lower socioeconomic status, family history of seizures or other neurologic disease, conception after infertility treatment, maternal thyroid disease, severe pre-eclampsia, bleeding during pregnancy, viral illness, abnormal placenta, intrauterine growth retardation, and postmaturity.
Intrapartum risk factors included maternal pyrexia, persistent occipitoposterior position, and acute intrapartum events. Operative vaginal delivery and emergency cesarean section were risk factors whereas elective cesarean carried a reduced risk. Intrapartum hypoxia was absent in >70% of cases of NE.
Causes of newborn encephalopathy are heterogeneous and almost 70% have only antepartum risk factors; 24% have both antepartum and intrapartum factors; 5% have only intrapartum factors; and 2% have no recognizable risk factors. [1, 2]
COMMENT. The majority of causes of neonatal encephalopathy occur in the antepartum period and are not primarily birth-related. Elective ceasarean section is associated with a reduced risk of NE, presumably by avoidance of some intrapartum risk factors, including post-maturity, maternal pyrexia, bleeding, and acute labor events.