experts say that the "crack baby" stigma was more harmful than the PCE. Teachers were affected by these cultural stereotypes; such biases may have negatively affected the educational experiences of children thus stigmatized. Teachers who knew that specific children had been exposed to crack in utero may have expected these children to be disruptive and developmentally delayed. Children who were exposed to cocaine might be teased by others who knew of the exposure, and problems these children had might be misdiagnosed by doctors or others as resulting from PCE when they may really have been due to factors like illness or abuse. The social stigma of the drug also complicated studies of PCE; researchers labored under the awareness that their findings would have political implications. In addition, the perceived hopelessness of 'crack babies' may have caused researchers to ignore possibilities for early intervention that could have helped them. The social stigma may turn out to be a self-fulfilling prophecy. Research Confounding factors A number of the effects that had been thought after early studies to be attributable to prenatal exposure to cocaine are actually due partially or wholly to other factors, such as exposure to other substances (including tobacco, alcohol, or marijuana) or to the environment in which the child is raised. PCE is very difficult to study because of a variety of factors that may confound the results: pre- and postnatal care may be poor; the pregnant mother and child may be malnourished; the amount of cocaine a mother takes can vary; she may take a variety of drugs during pregnancy in addition to cocaine; measurements for detecting deficits may not be sensitive enough; and results that are found may only last a short time. Studies differ in how they define heavy or light cocaine use during pregnancy, and the time period of exposure during pregnancy on which they focus (e.g. first, second, or third trimester. Drug use by mothers puts children at high risk for exposure to toxic or otherwise dangerous environments, and PCE does not present much risk beyond these risk factors. PCE is clustered with other risk factors to the child, such as physical abuse and neglect, domestic violence, and prenatal exposure to other substances. Such environmental factors are known to adversely affect children in the same areas being studied with respect to PCE. Most women who use cocaine while pregnant use other drugs too; one