Johnson, S. F., R. J. McCarter (U. of Maryland School of Medicine, Baltimore, MD 21201), and C. Ferencz. Changes in alcohol, cigarette, and recreational drug use during pregnancy: implications for intervention. Am J Epidemiol 1987;126:695–702. From the Baltimore-Washington infant Study, a regional epidemiologic study of congenital cardiovascular malformations, 1,336 mothers of infants selected as controls (a representative sample of the area birth cohort enrolled between April 1, 1981 and September 1, 1984) were studied with respect to alcohol, cigarette, and recreational drug use prior to and during pregnancy. Nearly half of the 1,336 women abstained from any substance use during pregnancy. Of the remainder, half restricted substance use to only alcohol or cigarettes. Only cigarette smokers showed a majority (68.5%) of women falling to successfully quit during pregnancy. Cigarette and recreational drug use during pregnancy was associated with lower socioeconomic status, while alcohol use was associated with higher social status. Cessation of cigarette and recreational drug use was more common among professionals and the college-educated, but these same characteristics, along with higher income, were associated with failure to quit drinking. Younger women were less likely to use alcohol and cigarettes and more likely to success fully quit these habits once adopted. Use of alcohol and tobacco was greater among whites, and recreational drug use was greater among black women, but race was not associated with quitting use of any substance. Length of time trying to become pregnant and the mothe's perceived health were not found to be associated with substance use or quitting. This sociodemographic profile suggests subgroups which must be targeted for intervention by the prenatal care provider, as well as intervention stategies.