Children exposed to cocaine before birth show subtle but discernible differences in their ability to plan and problem-solve once they reach school age, University of Florida researchers report.
Still, most fare far better in the first few years after birth than many experts once predicted, contradicting the notion that as a rule, cocaine-exposed infants would be born with devastating birth defects or miss major developmental milestones.
"I think the early information we had was that these children might be irreversibly damaged - that they would potentially have lots of problems in school, that they might have lots of behavior problems, that they might have problems thinking and learning," said UF neonatologist Marylou Behnke, M.D.
Instead, UF researchers write in the April online issue of the Journal of Pediatric Psychology, prenatal cocaine exposure is linked to smaller head circumference at birth and to less optimal home environments, which in turn have direct yet mild effects on developmental outcome at 3 years of age. Those effects persist at ages 5 and 7, once more demands are placed on the children during the formal school years, according to related findings the researchers presented at the recent annual meeting of the Society for Research in Child Development.
"We have found that at age 3, the more cocaine the child was exposed to, the smaller the head circumference at birth, and the smaller the head circumference at birth, the worse the developmental or cognitive outcomes," said Behnke, adding that head circumference at birth is an important measure because generally the head grows as brain size increases. "So cocaine is not directly affecting outcome, but it affects this intermediary measure that we're looking at that then goes on to affect outcome. We think that head circumference may be some sort of a marker for what is going on in the prenatal environment, that it's a proxy marker for other things."
Each year, about 45,000 infants who were exposed to cocaine in the womb are born, according to the National Institute on Drug Abuse. When the dangers of prenatal cocaine exposure first grabbed headlines in the mid-1980s, no studies had followed children beyond infancy. UF researchers began studying crack and cocaine users and their offspring about 13 years ago, launching a study funded by the National Institute on Drug Abuse that assesses physical and developmental outcomes among 300 children from birth on. Half the study participants were exposed to cocaine in utero, half were not; all were from rural areas of north Central Florida.
Average daily cocaine use among the 154 mothers who used drugs throughout pregnancy was $32.70, the cost equivalent of approximately three rocks of crack cocaine. Of that group, one quarter were considered "heavy users."
"We have found in our developmental studies of our newborns that there were some subtle differences between the groups, not the kind of things that moms and dads would notice particularly, not the kinds of things that family members might suspect if they saw the baby," said Behnke, a professor of pediatrics at UF's College of Medicine. "As the children have started to get older, we have begun to see a few more subtle effects, so by the time they were at six months, we could see some effect of cocaine on their developmental processes, but again, we're not talking about dramatic effects. And as they moved on to age 3, we began to see even more effects."
Cocaine-exposed children were assessed at age 3 in part by using the standardized assessment known as the Bayley Scales of Infant Development, which assesses a child's ability to perform age-appropriate functions such as following simple directions and completing puzzles and other problem-solving tasks. At 5 and 7, more extensive neuropsychological and intelligence testing was done.
"Some kids just have trouble getting going, getting started and once they get going they do a little better," said co-researcher Fonda Davis Eyler, a UF professor of pediatrics. "Others have trouble maintaining their attention and they respond to other cues and not what they're supposed to be targeting on and doing, or they only have simple strategies, not more complex ones."
The quality of the home environment was even more likely than smaller head size to influence outcome, Eyler said. UF researchers have analyzed measures of depression and self-esteem among caregivers and studied their views on parenting and child development. Children living in nurturing environments with supportive, competent caregivers scored higher on developmental measures, even when they had been exposed to cocaine before birth.
The children participating in the study are now entering the pre-teen years. As their academic responsibilities and social pressures increase, other, more serious effects may surface, Eyler said. Meanwhile, researchers are increasingly able to refine the tests they use to more precisely assess the children's progress, homing in on the areas of the brain more involved with planning and thinking strategically - the regions that cocaine, in theory, would most likely affect.
In this next arm of the study, all will undergo intelligence and achievement tests, including assessments of language ability, attention, problem-solving and abstract thinking, Eyler said. Researchers also will ask the youngsters about their attitudes, behavior, family relationships and friendships. In addition, they will assess the children's home environment and interview their caregivers and schoolteachers.
Deborah A. Frank, M.D., a professor of pediatrics at Boston University School of Medicine, said the UF team's work will "do much to dispel the inaccurate and hysterical predictions that inaccurately stigmatize children with intrauterine cocaine exposure."
"This is an important contribution to the field, since it thoughtfully addresses both biologic and social risk factors, viewing intrauterine cocaine exposure as only one of many possible influences on children," Frank said. "The importance of positive environmental characteristics in promoting toddler development, regardless of intrauterine cocaine exposure, is a crucial finding of this work that can guide evidence-based interventions for families.
"Although these findings are reassuring, long-term follow-up of this sample will be important, since intrauterine exposures such as tobacco and marijuana have been shown to have 'sleeper' effects on development that do not emerge until adolescence," she added.