When the "crack epidemic" began 20 years ago, loud alarms were sounded by the media. "Crack babies", it was said, would never truly recover from their pre-birth experiences, no matter how many interventions were provided for them-- nor would babies exposed to other pharmaceutically-active substances, even needed prescription drugs. Analogies were drawn from physical defects produced by exposure to toxins or disease at critical periods early in prenatal development, and especially from studies on animals experimentally exposed to harmful substances like alcohol.
All this concern made some sense, in the light of the sketchy evidence available. If there are two kinds of mistakes you can make, and one has more serious consequences than the other, you're better advised to make the less harmful mistake. In the case of prenatal drug exposure, the more potentially harmful mistake would be to assume without evidence that prenatal drug use did NOT seriously damage babies.
Much less damage would be done by assuming that prenatal drug use would cause problems for embryonic or fetal development; even if this turned out to be wrong, there would be no harm to the babies, because babies clearly do not need drug exposure for good development. However, it would be a mistake to think that no harm at all would potentially result from this error, because (for instance) efforts to prevent drug use by pregnant women could use up resources better expended on other interventions. There are always possible negative consequences of decisions, even those that appear most morally justified.
Some years after the first reports about the "crack epidemic", however, more searching questions began to be asked, as empirical research showed that many drug-exposed babies-- ones who received excellent nurture--- actually developed quite normally. New reports began to declare, "crack babies aren't broken". New research efforts began to investigate relationships between prenatal drug exposure and behaviors or abilities that are most characteristic of human beings, behaviors that are difficult to test in animals.
A recent study by Bergin and McCullough (Bergin, C., & Mccullough, P. . Attachment in substance-exposed toddlers: The role of caregiving and exposure. Infant Mental Health Journal, Vol. 30, pp. 407-423) investigated characteristics of the babies of 41 low-income mothers who had used alcohol, cocaine, and other substances while pregnant. These 41 babies were compared to a group of other babies who were matched with them on factors like birth weight that increase the risk of developmental problems, but who were not exposed to drugs prenatally. All of the babies were tested at 12 months on the quality of their attachment to their mothers, and the mothers were tested on their sensitivity and involvement (this latter assessment was based on two hours of videotaped interaction between each mother and her baby).
To simplify the matter a bit, Bergin and McCullough's study asked this: Were the babies' attachment behaviors most strongly influenced by their prenatal exposure to drugs and alcohol? Or was attachment most affected by the mothers' sensitivity to and involvement with the babies? In answer to these questions, one important point was that neither group of babies did as well as might ordinarily be expected from babies of middle-class families. Their lives in poverty caused risks for all of them, whether drug-exposed or not.
Beyond the risks inherent in poverty, though, the prenatal drug exposure apparently had little effect on the babies' later attachment behavior. It was the nurturing behavior of the mothers that had the real impact. Mothers who displayed sensitivity to their babies' signals and who involved themselves in social interaction with the babies were the ones whose babies showed healthy development of attachment. This conclusion was supported by the fact that even the amount of drug exposure had little or no impact on the babies' attachment (you might expect that heavy exposure would cause more problems than less exposure). Bergin and McCullough noted that although animal studies showed the effects of prenatal drug exposure, "Perhaps there are fetal programming effects from substance exposure, but in humans, these effects may be small when compared with social experience."
Of course, as in any study of this kind, there are questions to be asked about the interpretation of the results. Take, for example, the idea that maternal sensitivity is responsible for good development of attachment. The actual situation may be a much more complicated one, in which babies who are becoming securely attached tend to behave in ways that are easy for their mothers to understand, and respond so enthusiastically to their mothers' social play that the mothers are encouraged to interact even more. But in any case it remains clear that prenatal drug exposure was not much of a factor in determining this aspect of development.
Several thoughts occur when we consider this study's results. One is that concerns about development of adopted children need to focus on the nurturing care they have received, more than on drug exposure that has not had obvious physical effects. Another is that, if these results can be generalized to antidepressant drugs, care of women with a history of depression may need to focus on improving their sensitivity to their babies' social signals. Finally, it may be best to spend resources on "saying yes" to supporting abilities for good nurturing rather than simply "saying no" to drugs.