Maternal drinking during pregnancy was divided into 5 exclusive categories: 1-10 days of use during the pregnancy, 11-35 days of use during the pregnancy, more than 35 days of use during the pregnancy, ‘some heavy use’ (i.e., at least 5-6 drinks on the days that they typically drank and having 5 or more drinks in a single day at least 1 day a month), and ‘frequent heavy use’ (i.e., ‘some heavy use’ plus having 5 or more drinks in a single day at least 2-3 days a month). Maternal smoking during pregnancy was first divided into two categories: light/moderate smoking (1-10 cigarettes per day) during the 1st trimester and beyond the first trimester, and heavy smoking (11+ cigarettes per day) during the 1st trimester and beyond the first trimester. If a mother stopped smoking at a certain point in her pregnancy, her data was included in the appropriate category. For example, if she quit after 1 month of the pregnancy, she would be counted as having smoked during the first trimester, and if she quit after 4 months, she would be counted as having smoked beyond the first trimester.
