Intrapartum risk factors for newborn encephalopathy: the Western Australian case-control study.
OBJECTIVE
To identify intrapartum predictors of newborn encephalopathy in term infants.


METHODS
Population based, unmatched case-control study.


METHODS
Metropolitan area of Western Australia, June 1993 to September 1995.


METHODS
All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.


METHODS
Adjusted odds ratio estimates.


RESULTS
The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. Maternal pyrexia (odds ratio 3.82), a persistent occipitoposterior position (4.29), and an acute intrapartum event (4.44) were all risk factors for newborn encephalopathy. More case infants than control infants were induced (41.5% and 30.5%, respectively) and fewer case infants were delivered by caesarean section without labour (3.7% and 14.5%, respectively). Operative vaginal delivery (2.34) and emergency caesarean section (2.17) were both associated with an increased risk. There was an inverse relation between elective caesarean section (0.17) and newborn encephalopathy. After application of a set of consensus criteria for elective caesarean section only three (7%) eligible case mothers compared with 33 (65%) eligible control mothers were sectioned electively. Of all the case infants, 113 (69%) had only antepartum risk factors for newborn encephalopathy identified; 39 (24%) had antepartum and intrapartum factors; eight (5%) had only intrapartum factors; and four (2%) had no recognised antepartum or intrapartum factors.


CONCLUSIONS
The causes of newborn encephalopathy are heterogeneous and many relate to the antepartum period. Elective caesarean section has an inverse association with newborn encephalopathy. Intrapartum hypoxia alone accounts for only a small proportion of newborn encephalopathy. These results question the view that most risk factors for newborn encephalopathy lie in the intrapartum period.
Badawi
N
N
TVW Telethon Institute for Child Health Research, PO Box 855, West Perth, Western Australia 6872, Australia. nadiaBnch.edu.au
Kurinczuk
J J
JJ
Keogh
J M
JM
Alessandri
L M
LM
O'Sullivan
F
F
Burton
P R
PR
Pemberton
P J
PJ
Stanley
F J
FJ
D001238:Asphyxia Neonatorum / Q000453:epidemiology; D001927:Brain Diseases / Q000453:epidemiology* / Q000209:etiology; D016022:Case-Control Studies; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D005311:Fetal Hypoxia / Q000453:epidemiology; D005334:Fever / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D007744:Obstetric Labor Complications / Q000453:epidemiology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012307:Risk Factors; D014904:Western Australia / Q000453:epidemiology