Infection and Birth Weight

Extremely low-birth weight infants, the tiniest category of premature infants, are much more likely to experience developmental impairments if they acquire an infection during the newborn period, according to a study by the Neonatal Research Network of the National Institute of Child Health and Human Development (NICHD). The developmental impairments were seen regardless of whether the infection occurred in the brain, blood or intestines (Journal of the American Medical Association, Nov. 17, 2004).

During their hospitalizations after birth, 65 percent of a group of extremely low-birth weight infants had developed at least one infection, according to the study conducted by Barbara Stoll, MD, and a colleague at the Emory University School of Medicine in Atlanta, GA. The infants were more likely to have an impairment than those who had not developed an infection.

"Successfully treating an extremely low-birth weight infant's infection does not automatically ensure that the infant will do well," said NICHD director Duane Alexander, MD. "Parents and health care workers need to monitor these children carefully as they grow and be ready to provide them with developmental and educational services if necessary."

A total of 60,326 infants with very low birth weight were born in 2002, or 1.46 percent of the 4,021,726 total births for that year, according to the U.S. Centers for Disease Control and Prevention. A low birth weight is less than 2,500 grams (about 5.5 pounds), and a very low birth weight is less than1,500 grams (about 3.3 pounds).

In the current study researchers analyzed the records of infants with extremely low birth weight.  Yearly statistics for these infants, weighing less than 1,000 grams (2.2 pounds), are not compiled. However, study co-author Rosemary Higgins, MD, of the Pregnancy and Perinatology Branch at NICHD, estimated that as many as 50 percent of newborns below 1,500 grams may fall into that category.

The study enrolled infants weighing 401 to 1,000 grams at birth. A total of 6,093 infants were evaluated for the study. The infants were evaluated when they were between 18 and 22 months corrected gestational age. The majority of the infants (65 percent) had at least one infection during their stay in the hospital after birth, the researchers found.

Approximately 47 percent of the children with infections had some form of developmental delay or physical or mental impairment, according to Dr. Higgins. Impairments included cerebral palsy and visual and hearing impairments or were manifested as low scores on tests of infant mental development or motor skills.

Although infants with infections were more likely to have such impairments, those without infections also had a high rate of impairment (29 percent), Dr. Higgins noted. "This is a high-risk, fragile population of infants."

As expected, meningitis-an infection of the membrane covering the brain and spinal cord-was associated with neurological impairments. For example, in the group that had meningitis with or without the blood infection sepsis, 38 percent had low scores for mental development, compared to 22 percent of the children who did not have an infection. Children in this group also were more likely to have cerebral palsy (19 percent) than were children who did not have an infection (8 percent).

Moreover, children with infections that did not directly involve the nervous system were more likely to have an impairment involving the nervous system.

Of the infants with sepsis alone, 37 percent had low mental development scores, and 17 percent had cerebral palsy. Among the children without an infection, 22 percent had low mental development scores, and 8 percent had cerebral palsy. Of the infants who had both sepsis and the intestinal infection necrotizing enterocolitis, 42 percent received low mental development scores, compared to 22 percent who had not had an infection.

Prior to the current study, researchers had known that infants with extremely low birth weight were more likely to experience problems with the brain and nervous system but did not know the extent of the problems, Dr. Higgins explained. This study is the first to show how widespread the problems are and that they appear more often in children who have had an infection.

The authors called for additional research to determine how infections might injure brain tissue in this group of infants, as well as research to prevent infection and nervous system damage resulting from an infection.


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