Infection Puts Extremely Low Birth Weight Infants at Risk For Developmental Delays
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, one of the National Institutes
of Health. The developmental impairments were seen regardless of
the type of infection whether it occurred in the brain, blood or
The study was conducted by Barbara J. Stoll, M.D., of the Emory
University School of Medicine in Atlanta, Georgia and her colleague.
Appearing in the November 17 Journal of the American Medical Association,
the study reported that 65 percent of a group of extremely low birth
weight infants had developed at least one infection during their
hospitalizations after birth. These infants were more likely to
have an impairment than were infants who had not developed an infection.
"This study shows us that 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,
M.D. "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."
According to the U.S. Centers for Disease Control and Prevention,
there were 60,326 very low birth weight infants born in 2002, or
1.46 percent of the 4,021,726 total births for that year. Infants
are classified as low birth weight if they are born weighing less
than 2500 grams (about 5.5 pounds) and very low birth weight if
they weigh less than1500 grams (about3.3 pounds). In the current
study, the researchers analyzed the records of extremely low birth
weight (ELBW) infants those weighing less than 1000grams, or 2.2
pounds. Yearly statistics are not compiled on ELBW infants. Study
co-author Rosemary Higgins, M.D., of NICHD's Pregnancy and Perinatology
Branch, estimated that as many as 50 percent of newborns below 1500
grams may fall into the ELBW category.
The study enrolled infants weighing from 401 to 1000 grams at birth.
In all, 6,093 infants were evaluated for this study. The infants
were evaluated when they were between 18 and 22 months corrected
gestational age equivalent to the age they would be had they been
born at term. The researchers found that the majority of these infants
(65 percent) had at least one infection during their stay in the
hospital after birth.
According to Dr. Higgins, about 47 percent of the children with
infections had some form of delay in development or a physical or
mental impairment. These impairments consisted of either cerebral
palsy, a visual impairment, a hearing impairment, or were manifested
as low scores on tests of infant mental development or motor skills.
Dr. Higgins added that although infants with infections were more
likely to have such impairments, infants who did not have infections
also had a high rate of impairment, at about 29 percent.
"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 sepsis
(an infection of the blood) 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 were also 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 also more likely to have an impairment involving
the nervous system. Of the infants who had sepsis alone, 37 percent
had low mental development scores and 17 percent had cerebral palsy.
Of 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 necrotizing enterocolitis (an intestinal
infection), 42 percent received low mental development scores, compared
to 22 percent who had not had an infection.
Dr. Higgins explained that before the current study, researchers
had known that ELBW infants were more likely to experience problems
with the brain and nervous system, but did not know the extent of
the problems. 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 study 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 to prevent such nervous
system damage from occurring once an infection had occurred.
The NICHD is part of the National Institutes of Health (NIH),
the biomedical research arm of the federal government. NIH is an
agency of the U.S. Department of Health and Human Services. The
NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. NICHD publications, as well
as information about the Institute, are available from the NICHD
Web site, http://www.nichd.nih.gov,
or from the NICHD Information Resource Center, 1-800-370-2943; e-mail