Twin pairs ranged in age from 11 to 23 years, with an average of 15.15 years. 4.6% of mothers met criteria for alcohol dependence (AlcD), 8.9% of mothers for alcohol abuse (AlcA), and based on maternal history report, 19.4% of fathers for AlcD. With regard to smoking, 37.1% of mothers and 40.1% of fathers were regular smokers (defined by twin report); moreover, 37% of mothers reported smoking during the 1st trimester and 21% continued to smoke beyond the 1st trimester. 24% of mothers reported drinking 1-10 days during pregnancy, 3% drank 11-35 days, less than 1% (0.7%) reported drinking on more than 35 days of the pregnancy. Further, some heavy use was reported by 2.5% of mothers and frequent heavy use was reported by 1% of the sample.
