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Prenatal Cocaine Exposure Has Lingering Cognitive Effects

But home environment may play a bigger role, new research says

TUESDAY, May 25, 2004 (HealthDayNews) -- The long-term consequence of cocaine exposure in the womb may not be as dire as once predicted, but it can still cause cognitive impairment and a reduced likelihood of an above-average IQ.

That's the conclusion of new research, published in the May 26 issue of the Journal of the American Medical Association, which also found that a positive home environment can make a difference to such kids.

"While prenatal cocaine exposure is not as devastating as was once thought, there are significant deficits in areas of intellectual functions that are important later in life, and these deficits are there even when you control for environmental effects," said study author Lynn Singer, deputy provost at Case Western Reserve University in Cleveland.

When a mother ingests cocaine during pregnancy, the drug passes through the placenta, enters the baby's bloodstream and passes through the fetal brain barrier, according to the study. Some studies on the long-term effects of such exposure haven't found an association between cocaine and deficits in cognitive development, while others have found cocaine exposure negatively affects cognitive development.

For this study, the researchers recruited almost 400 pregnant women from a large urban teaching hospital, all of whom were believed to be at high risk for drug use. Once they'd given birth, tests revealed that 190 of the babies had been exposed to cocaine in utero, while 186 had not.

The children were assessed at 6, 12 and 24 months. When they were 4 years old, they were tested using the Wechsler Preschool and Primary Scales of Intelligence-Revised. Along with IQ scores, this test also provides information on arithmetic, vocabulary, verbal comprehension, object assembly, block design and picture completion skills. None of the researchers administering the tests knew which children had been exposed to cocaine in utero.

The children's primary caregivers were also asked to complete a questionnaire to help the researchers assess the quality of the home environment.

The researchers found overall IQ scores were not significantly different between the cocaine-exposed children and the non-exposed youngsters. The children exposed to cocaine, however, were 74 percent less likely to have an above-average IQ, and their scores on some of the subtests were also significantly lower.

However, those children who were exposed to cocaine but raised in foster or adoptive care had higher IQ scores than cocaine-exposed kids who were raised by their biological mothers or a relative. In fact, the researchers found, their full-scale IQ scores were one point higher than those of non-exposed children.

But Singer pointed out this difference was most significant when you looked at children who scored under 70 on the full-scale IQ, because less than 70 is the line of mental retardation and kids with scores that low may never function independently.

Twenty-five percent of the cocaine-exposed children raised by their mothers or a biological relative scored under 70, while only 10 percent of the cocaine-exposed children raised in foster or adoptive care did.

"In utero cocaine exposure definitely causes some sort of insult to the fetal brain, and the higher the exposure, the greater the insult," said Dr. Ernest Krug, head of the Center for Human Development at William Beaumont Hospital in Royal Oak, Mich.

"But positive environmental exposure can modify this brain insult. It really appears that the environment does have a critical impact on these kids. The brain has an amazing ability to lay down new pathways if the environment is stimulating and allows it to happen," Krug added.

"Home environment appears to be a major determining factor," said Dr. Harley Ginsberg, medical director of the Neonatal Intensive Care Unit at Ochsner Clinic Foundation Hospital in New Orleans.

To help youngsters who have been exposed to cocaine in utero, Ginsberg said it might be "more advantageous to increase support services to the home. We can't undo what went on during pregnancy, but we can alert social services and the baby's pediatrician, and get drug counseling folks in touch with the mother. With close follow-up and a review of the environment, we can still have a big impact and help this baby do well."

More information

To learn more about the effects of cocaine use during pregnancy, visit the March of Dimes or the Substance Abuse and Mental Health Services Administration.

SOURCES: Lynn Singer, Ph.D., deputy provost and professor, pediatrics and general medical science, Case Western Reserve University, Cleveland; Ernest Krug, M.D., head, Center for Human Development, William Beaumont Hospital, Royal Oak, Mich.; Harley Ginsberg, M.D., medical director, Neonatal Intensive Care Unit, Ochsner Clinic Foundation Hospital, New Orleans; May 26, 2004, Journal of the American Medical Association
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