The substances a mother puts in her body during pregnancy nearly always reach her developing baby. The long-term effects of illegal drugs can often present problems for these children.
A recent study found that teens showed some issues in thinking skills and behavior if they were exposed to cocaine before birth.
The teens' brains also showed some slightly different structures, though these differences did not appear to change the way the brain worked.
The teens showed some behavior difficulties and poorer scores in memory and language tests.
The study, led by Stacy Buckingham-Howes, PhD, of the Department of Pediatrics at the University of Maryland School of Medicine, aimed to find out whether teens who had been exposed to cocaine in the womb had any behavior or cognitive problems.
The researchers combed through four databases to locate all studies through July 2012 that were related to drug use during pregnancy and the behavior of the resulting children as adolescents.
The researchers identified 27 studies which included a total of nine different groups which had been reviewed.
These studies reported on findings related to the teens' behaviors, cognitive or school performance, brain structure or function and physical body responses.
Of the 11 studies that reported results on the teens' behavior, seven found small differences between the children who had been exposed to cocaine before birth and those who had not, but the differences varied.
In four studies, being exposed to cocaine prenatally was linked to attention problems and externalizing and internalizing behaviors.
Externalizing problems refers to behavior issues like acting out, aggression, rule-breaking and hyperactivity. Internalizing problems refers to issues like depression, anxiety and antisocial behavior.
The teen girls who had been exposed to cocaine before birth also showed more anxiety and depression than girls without prenatal cocaine exposure.
Of the eight studies that looked at teen's school performance or cognitive (thinking) skills, six found lower scores on tests related to language and memory among the teens who had been exposed to cocaine while in the womb.
The amounts varied across these studies, but they were significant enough that they could not be considered chance or coincidence.
Eight of the studies reported results on brain structure and functions. They found some small physical differences in the brain structure of teens with prenatal cocaine exposure.
However, these differences did not appear to translate into different brain functions for these teens.
The three studies that reported on physiological differences did not find similar results, so there was not enough information to determine patterns in teens' biology if they were exposed to cocaine before birth.
The majority of the studies included in the analysis did make adjustments to account for other factors that could influence children's behavior or cognitive performance.
These factors included other things the kids had been exposed to before birth, the environment they grew up in and how much violence they had been exposed to.
"Consistent with findings among younger children, prenatal cocaine exposure increases the risk for small but significantly less favorable adolescent functioning," the authors wrote.
"Although the clinical importance of differences is often unknown, the caregiving environment and violence exposure pose additional threats," they wrote.
This study was published May 27 in the journal Pediatrics.
The research was funded by the National Institute on Drug Abuse at the National Institutes of Health. The authors declared no conflicts of interest.