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Maternal infections associated with increased risk of cerebral palsy



VANCOUVER, B.C. – Intra- or extra-amniotic fluid infections during pregnancy are associated with an increased risk of having a child with cerebral palsy, according to analysis of six million California birth records.

Researchers found that pregnant women who were hospitalized with diagnosis of chorioamnionitis had a fourfold increase in risk of having a child with cerebral palsy (CP), while genitourinary and respiratory infections increased that risk by twofold, each.

"I think this is a very important study, and it took us a step further in trying to understand what could cause cerebral palsy," said Dr. Lee M. Sanders, associate professor of pediatrics and codirector of the Center for Policy, Outcomes, and Prevention at Stanford (Calif.) University. But because the study shows an association only, "it’s important not to cause alarm," said Dr. Sanders, who was not involved in the study.

Dr. Joshua Bear of the University of California, San Francisco, and his colleagues analyzed the California birth records from 1991 to 2001, in addition to records of all children receiving services for CP from the California Department of Developmental Services through 2006.

There were close to 8,500 CP cases, or 1.4 per 1,000 live births, which is at the lower end of some of the reported statistics, Dr. Bear said.

Analysis of infection diagnoses showed that 6% of the women had unaffected births, while 15.3% had children with CP, with a relative risk of 2.7. Among the latter group, 7.6% had chorioamnionitis, 5.2% had other genitourinary infections, and 3.5% had respiratory infections.

Among women hospitalized with chorioamnionitis, there was a fourfold increase in risk of having CP in preterm infants and twofold increase in term births. Most women hospitalized with chorioamnionitis gave birth at that hospitalization, said Dr. Bear.

For other genitourinary infections, there was a 1.4-fold increase in the risk of CP for prenatal hospitalization, and 1.9-fold increase for birth hospitalization.

Respiratory infections showed a similar trend, with a twofold increased risk for prenatal hospitalization and 2.6-fold increase risk for birth hospitalization.

Increased risk of CP with other genitourinary and respiratory infections, even during prenatal hospitalization, suggest that "these infections may be directly or indirectly contributing to harm on the developing fetal brain and not be simply another complication during delivery," Dr. Bear said during his presentation at the annual meeting of Pediatric Academic Societies.

Analysis of sociodemographic risk factors showed that women younger than 18 and older than 35 were more likely to have a child with CP. Black women were at a higher risk of CP, compared with white and Hispanic women, and Asian women were at lower risk. Years of education was inversely associated with the risk of CP. Also, male infants were at a slightly higher risk of CP than were their female counterparts.

Yet when researchers adjusted for maternal age, race, education, socioeconomic status, and infant sex, the association between infections and increased risk of CP remained the same.

Dr. Bear and his colleagues also stratified the data by presence of birth asphyxia, to find clues if it could be a cause for CP. The results showed a large drop in rate ratios of chorioamnionitis, from 4 to 1.5 when asphyxia was diagnosed at birth, but the rates for other genitourinary and respiratory infections remained the same. "This suggests that there’s some interaction between chorioamnionitis and presence of birth asphyxia, although the nature of that interaction is unclear." said Dr. Bear.

The study had several limitations, including the use of ICD-9 codes, researchers’ inability to account for comorbid conditions related to hospitalization, and being limited to hospital-based diagnoses.

The findings, said Dr. Bear, highlighted the need for further research in several areas, including the association between CP and respiratory infections, and whether risk of CP can be decreased by preventing or treating the infections.

The findings can also "help us with public health interventions, such as better rates of influenza vaccinations among pregnant women," said Dr. Sanders.

Dr. Bear and Dr. Sanders had no relevant disclosures.

On Twitter @naseemmiller

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