Intrapartum Fever Is Associated With Neonatal Encephalopathy


WASHINGTON — Isolated intrapartum fever and chorioamnionitis are independent risk factors for neonatal encephalopathy, Heidi Blume, M.D., said at the annual meeting of the Pediatric Academic Societies.

“It remains unclear if fever is the cause of injury, exacerbates injury, or is a sign of some other noxious process,” said Dr. Blume of the University of Washington, Seattle.

Neonatal encephalopathy, which affects up to 6 in 1,000 term infants annually, is a clinically defined syndrome of disturbed neurologic function during the infant's earliest days of life. Symptoms include difficulty initiating and maintaining respiration; depressed tone and reflexes; subnormal level of consciousness; and, sometimes, seizures.

Dr. Blume undertook a population-based, case-control study of infants born in Washington from 1994 to 2002. She used data from the Washington State Birth Registry; this information is linked to the state's Comprehensive Hospital Abstract Reporting System. The system includes discharge diagnoses, diagnosis and procedure codes, and dates of hospitalization.

The 1,114 cases were singleton term infants whose ICD-9 discharge diagnoses included birth asphyxia, newborn convulsions, central nervous system dysfunction, or other cerebral irritability.

These cases were matched with 6,046 control infants. Exposure to isolated fever was defined as maternal intrapartum fever of 38° C or greater, or ICD-9 diagnosis of maternal intrapartum pyrexia without chorioamnionitis.

Exposure to chorioamnionitis was defined by ICD-9 diagnosis of chorioamnionitis or infection of the amnion.

Mothers of encephalopathy cases were more likely to be of low socioeconomic status, to be nulliparous, and to have had preeclampsia.

Case infants were more likely to have received late prenatal care and to be of low birth weight, and slightly more likely to be male, according to the researcher.

Both isolated maternal fever and chorioamnionitis were more common in encephalopathy cases than in controls. Exposure to maternal fever reportedly occurred in 2.5% of the controls and 8% of cases, for an adjusted odds ratio of 3.2. Chorioamnionitis was present in 1.2% of controls and 6% of cases, for an adjusted odds ratio of 5.7.

“These relationships persisted in subgroups of cases who were diagnosed with seizures and birth asphyxia,” Dr. Blume said at the meeting, sponsored by the American Pediatric Society, the Society for Pediatric Research, the Ambulatory Pediactric Association, and the American Academy of Pediatrics.

Infants exposed to intrapartum maternal fever had a threefold increase in the risk of being diagnosed with seizure and a 3.5-fold increased risk of being diagnosed with birth asphyxia.

Infants exposed to chorioamnionitis had a fivefold increased risk of being diagnosed with seizure and almost a sevenfold increased risk of being diagnosed with birth asphyxia.

Dr. Blume noted some limitations in the study. She was not able to review charts, so it was impossible to determine what symptoms led to the diagnosis and discharge codes. However, she felt certain that few of the infants had meningitis, since the cases were limited to infants who were diagnosed during their newborn hospitalization, or who were admitted within 2 days of birth.

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