Consequences of Prenatal Drug Exposure: Opiates


Epidemiology of Opiate Use in Pregnancy

The literature regarding developmental outcomes for infants prenatally exposed to opiates is relatively sparse and was primarily generated in the 1970s and early 1980s. The literature is also made more problematic by the issue of polysubstance abuse, as research investigating prenatal opiate exposure includes exposure to heroin, methadone, or both, and may also include exposure to amphetamines, barbiturates, benzodiazepines, cocaine, alcohol, and nicotine. Recent studies report prevalence for opiate use during pregnancy to range from less than 1 to 2 percent to as high as 21 percent.

Growth/Physiological Effects

The most consistently reported effect of prenatal opiate exposure is associated with fetal growth retardation and neonatal abstinence syndrome. Neonatal abstinence is described by Kaltenbach and Finnegan () as a generalized disorder characterized by signs and symptoms of central nervous system hyperirritability, gastrointestinal dysfunction, respiratory distress, and vague autonomic symptoms that include yawning, sneezing, mottling, and fever. These early neurobehavioral outcomes do not persist, however.

Within the past decade, methadone maintenance has become accepted as the standard of care for opiate addiction during pregnancy. Methadone treatment stabilizes maternal drug levels and reduces the amount of poly drug use and associated complications. According to Kandall and colleagues (), no study has yet reported either a higher rate of malformations compared with control populations or an increase in any specific dysmorphic syndrome which could be related to maternal methadone use during pregnancy. Methadone treatment during pregnancy is associated with increased fetal growth and higher birth weights in offspring compared with heroin-exposed infants in earlier studies (), although these findings have not been supported by more recent studies.

Cognitive Effects

Studies on the early development of methadone-exposed offspring indicate relatively normal development, at least during infancy. In studies by Hans and her colleagues, no differences in mental development were found at four months, 12 months, and 24 months of age when comparing opiate-exposed and nonexposed children. Kaltenbach and Finnegan () found no differences in mental development scores at six months, 12 months, and 24 months when the two groups were compared. Between three and six years of age, heroin-exposed children performed more poorly than their peers on a cognitive index in one study, but the same on behavior and skills in another study. Kaltenbach () concludes her review of the effects of prenatal opiate exposure by stating that opiate-exposed infants through two years of age function well within the normal range of development and that children between two and five years of age do not differ in cognitive function from other high-risk populations.

Social and Environmental Considerations

Illicit drug use is associated with late and inadequate prenatal care, poverty, poor nutrition, domestic and stranger violence, and other severe threats to maternal and infant health. It is especially difficult to identify the impact of a specific illicit substance such as heroin due to the issue of polysubstance abuse. As with cocaine exposure, outcomes of heroin and methadone exposure are more strongly related to home and parenting environment variables than to direct drug effects.


Selections from the book: “Handbook of the Medical Consequences of Alcohol and Drug Abuse” (2004)