WEDNESDAY, Jan. 29, 2003 (HealthDayNews) -- Premature babies who experience even minor oxygen deprivation during or shortly after birth have lower IQs and poorer language skills, a new study says.
Researchers did a battery of tests to measure the intellectual abilities and language skills of 52 children, aged 5 to 6. All of the children had been born prematurely, defined as 36 weeks or less.
Half of the children were at slight to moderate risk of perinatal hypoxia, or oxygen deprivation, within two hours of birth. To measure this, the researchers used data on the babies' blood acidity. High acidity is a biochemical sign of reduced blood oxygen levels. Half of the newborns had no signs of oxygen deprivation.
Despite relatively minor differences in blood acidity, the two groups of babies showed significant differences in their language and intellectual skills as children, say the authors.
The pre-term group with mild to moderate levels of blood acidity scored 10 to 11 points lower on verbal and visuospatial tests than the low-risk pre-term group, a large discrepancy.
The study appears in the January issue of Neuropsychology. The researchers were from Wayne State University in Michigan, the University of Memphis, and Baptist Memorial Hospital in Memphis.
The study shows the threshold for problems associated with oxygen deprivation might be lower than thought, says Kathy Katz, a child psychologist and associate professor of pediatrics at Georgetown University.
"The study does suggest findings that are contrary to what has previously been believed," Katz says. "Previously, we believed it took a fairly substantial degree of hypoxia [oxygen deprivation] in order for there to be a later impact on cognitive function. This study suggests more mild hypoxia can have an impact."
Still, Katz adds, the study sample was small and more research is needed to confirm the findings.
"The findings are sort of surprising," she says. "Most studies have found newborns have a fair amount of resilience when deprived of oxygen."
The dangers to babies born prematurely is of increasing significance because so many more children are being born pre-term, according to the study.
In 2001, 12 percent of babies were born prematurely. That was the highest level in 20 years and was due in part to more multiple births, induced labor and older mothers, who are at higher risk of delivering prematurely.
"We need to be thinking about the fact that those babies may be at even higher risk than we thought," Katz says.
Previous research by the study authors found that full-term infants faced a similar risk.
In a 1999 study, the authors looked at 48 children who had mild to moderate hypoxia. Half of those children were born prematurely, while half were born full-term. The authors found the babies had poorer intellectual and verbal skills at age 6, regardless of whether they were born full term or prematurely.
The research was not able to show precisely what portion of the brain was damaged by the oxygen deprivation. One reason for this, the authors surmise, is that ultrasound, the typical way of looking at a baby's brain, is not powerful enough to detect subtle lesions.
More information
Here's a primer on premature babies from KidsHealth. Or check out this list of links to support groups, books and other resources for parents of premature babies.
