Cocaine use by pregnant women

Concerns about the adverse effects of maternal cocaine use during pregnancy on children exposed in utero have been the focus of many studies since the 1980s, when cocaine use began to increase, first among more affluent socioeconomic groups, then shifting to lower-income groups with the advent of cheap crack cocaine. During the mid to late 1980s, reports suggested that cocaine use during pregnancy caused congenital malformations, which were followed by other reports suggesting that cocaine had adverse effects on long-term neurodevelopment in children exposed in utero.

However, more recent systematic reviews of a large number of cases have not found an association between in utero exposure to cocaine and an increase in malformation of any kind, and these original concerns have not been borne out. Women who use cocaine have many other risk factors for poor neonatal outcome and adverse long-term effects on the child than women who don’t use cocaine, which may include low socioeconomic class, smoking, poor nutrition, and abuse of other drugs. Over the years, studies have been more carefully controlled for these other factors, comparing women who used cocaine during pregnancy to women in similar environment who had the same risk factors but did not use cocaine, and these studies have not found any association between maternal cocaine use and congenital defects or long-term effects in children.

In 2001, investigators performing a review of 36 prospective studies of prenatal cocaine exposure in children aged 6 years and younger found no convincing consistent evidence that in utero cocaine exposure was associated with negative effects on physical growth, developmental test scores, or receptive or expressive language. They concluded that “many findings once thought to be specific effects of in utero cocaine exposure can be explained in whole or in part by other factors, including prenatal exposure to tobacco, marijuana, or alcohol and the quality of the child’s environment”.

While these and later studies constitute the overall picture, some well-designed studies have suggested that prenatal cocaine exposure does have some serious adverse effects, most notably, a greater risk of prematurity and higher rates of placenta previa. There are also reports that some addicted women take high doses of cocaine near the end of pregnancy because they believe it may induce labor, which can result in placental bleeding and shock, potentially resulting in adverse, long-term effects on brain development in the baby.

An important consideration for obstetricians and other health care professionals who follow women who may use cocaine during pregnancy and those who follow their children is that continuing use of cocaine after a woman knows she is pregnant is recognized as essentially a sine qua non for addiction. Many  women may not disclose they use cocaine during a history, but our laboratory and others have developed methods of ascertaining whether a baby has been exposed to cocaine utero, such as analysis of neonatal hair and meconium, biomarkers for maternal cocaine use that are validated and widely used by social services and clinicians in the United States and Canada.

Cocaine and its metabolite benzoylecgonine accumulate in fetal hair during the last trimester, so a positive test is a strong indicator that the mother used cocaine during the sixth or seventh month. Cocaine and benzoylecgonine also accumulate in meconium, which is produced in mid-pregnancy, so a positive meconium test is an indication of use earlier in pregnancy. The meconium analysis can be used during the first few days post partum, while the hair analysis can be used for up to 3 months after the baby’s birth. Studies have documented damage to the brain in monkeys exposed in utero to cocaine at doses equivalent to doses that are typically used in humans.

Why similar findings have not been found in human studies speaks volumes to the plasticity of the newborn’s or young child’s brain and the ability to recover, if early environmental factors, with optimal stimulations, are favorable. This is an important area of research that is not yet fully resolved. They conducted a study comparing children exposed in utero to cocaine who had been adopted by stable families, where presumably, environmental factors were normal, with biological children of mothers from the same socioeconomic class.

The IQs of the adopted children were significantly lower than those of the comparator group, although the families were not aware of any neuro-developmental problems with the children. This suggests that even in an optimal situation, however, not all damage can be reversed by brain plasticity. Some studies have suggested that there may be an effect of fetal cocaine exposure on some specialized executive functions, such as the ability to perform complex tasks, or more refined functions, but the verdict on this issue is still out. Others continue to follow children who have been exposed in utero to cocaine, and are trying to understand sources of variability and why some children are affected and others are not.