A study published by Case Western Reserve University School of Medicine, MetroHealth Medical Center, and University Hospitals of Cleveland researchers in the April 17 issue of the "Journal of the American Medical Association," "Cognitive and Motor Outcomes of Cocaine-Exposed Infants," looks at how prenatal cocaine exposure affects child developmental outcomes. The study was conducted by Lynn T. Singer, Ph.D., Robert Arendt, Ph.D., Sonia Minnes, Ph.D., Ann Salvator, M.S., and H. Lester Kirchner, Ph.D., all of the CWRU School of Medicine, Department of Pediatrics; Kathleen Farkas, Ph.D., CWRU Mandel School of Applied Social Sciences; and Robert Kliegman, M.D., Medical College of Wisconsin, Milwaukee, Wis.
CWRU researchers followed 415 cocaine-exposed infants born at MetroHealth Medical Center in Cleveland to determine how prenatal cocaine exposure affects child developmental outcomes. They were compared to non-exposed infants on cognitive and motor development until age 2. What they found, according to Singer, was that prenatal cocaine exposure does affect a child's cognitive development, but not motor development. However, tobacco exposure had negative effects on motor development.
There have been previous studies in this area, but their findings are contradictory. While some studies have found generalized developmental delays in cocaine-exposed infants, other studies have not demonstrated differences or found only subtle cognitive effects. Those studies, CWRU researchers say, are flawed for several reasons, including high dropout rates, small sample sizes, ignored negative environmental factors, lack of biologic measures revealing exposure severity, incorrect sample populations and outdated development scales.
This study is the first to document the negative effects on cognitive development in a scientifically rigorous manner. Singer, professor of pediatrics and psychiatry, and interim provost and CWRU vice president, said the study was unique because it had measures of both the mothers' self report of their drug use prenatally, as well as infant meconium, which provided a physical measure of the amount of drug exposure. The study also controlled for many more factors in the environment than prior studies, including stimulation levels in the home, mothers' vocabulary and mental health status and characteristics of foster caregivers. The team used newly standardized versions of the major infancy development tests. And they were able to maintain more than 90 percent of the participants during the study, and at two years, 100 percent of the sample had at least one follow-up visit.
Mothers and infants were recruited between 1994 and 1996 from a high-risk population screened for drug use. Urine samples were obtained immediately before or after labor and delivery, and analyzed for the presence of cocaine metabolites, cannabinoids, opiates, PCP and amphetamines. Urine tests for drugs were performed by the hospital on all women who received no prenatal care, appeared to be intoxicated or taking drugs, had a history with the Department of Human Services in previous pregnancies, or self-admitted or appeared to be high risk for drug use after interview by hospital staff. Meconium was collected in the hospital from infants' diapers and screened for drugs.
Researchers initially identified 647 mothers and infants for the study, excluding 232 for various reasons. Infants were seen at the research laboratory at 6.5, 12 and 24 months and administered the widely used Bayley Mental and Motor Scales of Infant Development (BSID II) standardized assessments. The scales assigned infants a standard score reflecting memory, language and problem-solving abilities, as well as measurements of gross and fine motor control and coordination.
Researchers found that for all trimesters, cocaine-using women used alcohol, marijuana and tobacco more frequently and in higher amounts than non-users. Cocaine-using women were found to be older, had more children and were less likely to have had prenatal care. They also were less likely to be married; had lower vocabulary, block design and picture completion scores; and higher psychological distress scores.
The study also found that cocaine-exposed infants had lower gestational age, birthweight, head circumference and length than non-exposed infants. There were more preterm, low birthweight and small for gestational age infants in the exposed group.
Researchers also found that the rate of mental retardation in cocaine-exposed children at age 2 (13.7 percent v. 7.1 percent in the non-exposed group) is 4.89 times higher than expected in the general population. And the percentage of children with mild delays (37.6 percent in the exposed group v. 20.9 percent in the non-exposed group) requiring intervention was almost double the rate of the high risk, non-cocaine group. Researchers speculate it is likely that these children will continue to have learning problems and an increased need for special educational services at school age.
Another important note from the study is that cognitive delays could not be attributed to exposure to other drugs or a large number of other variables, including inadequate prenatal care, caregiver or birth mother intelligence, psychological distress, postnatal drug exposure or a low quality home environment.
Singer said the team is concerned that the study data will be misinterpreted and used to punish women or to remove children from their families.
"Prosecution of women will not address the problems of alcohol and drug abuse," Singer said. "In fact, our study indicates that tobacco exposure also has significant negative effects on infant development. Our findings also indicate that the quality of stimulation and environmental intervention can have a large effect on children's mental development independent of cocaine or other drug exposure."
About one million children have been born after fetal cocaine exposure since the mid-1980s, when the "crack epidemic" emerged with the marketing of a cheap, potent, easily available, smokeable form of cocaine.
"We hope that this study will convince public policy and health providers that there needs to be a major emphasis on the provision of drug treatment, including smoking cessation, and mental health services for women - especially poor women who are currently underserved," Singer said.
This study was supported by grants from the National Institute on Drug Abuse and the General Clinical Research Center.