Changing patterns of soft drug use prior to and during pregnancy: a prospective study.

Two hundred and seventeen women were interviewed during various stages of pregnancy to determine the extent and changing patterns of alcohol, nicotine and marihuana use in the year before pregnancy and during each trimester of pregnancy. Nutritional intake did not vary among women in the various drug using categories. Before pregnancy, 18% of the women were heavy social drinkers. During the first trimester this proportion was reduced by two-thirds and, in contrast to the other levels of social drinking, continued to decline during the last two trimesters. Age, income, education and smoking were all positively associated with heavy social drinking. Heavy cigarette smoking was reported by 13% of the women before pregnancy and by 8% during each of the trimesters. Education and income were negatively associated with heavy smoking. Three per cent of the women reported smoking more than five joints of marihuana per week before pregnancy and most continued to smoke marihuana heavily during pregnancy. The heavy marihuana users had a lower family income and less formal education than the overall sample. Marihuana use in general was associated with cigarette smoking and was not reported by women over 32 years of age. Except for heavy social drinking, soft drug habits at all levels of usage remained essentially unchanged after the first trimester. The likelihood of any one particular soft drug being reduced once pregnancy was established did not vary as a function of the concomitant use of other soft drug(s).