Cannabis Use During Pregnancy in France in 2010

Abstract

Cannabis is the most frequently used illicit drug in Western countries. France has among the highest frequencies, with 17% of those aged 15 to 34 years reporting its use. Data about cannabis use during pregnancy are scarce. This cross-sectional study was performed to estimate the proportion of women who reported cannabis use during pregnancy, analyze the demographic and social characteristics of users, as well as assess the association between cannabis use and preterm or small-for-gestational-age (SGA) birth. The study was conducted in France among a nationally representative sample of births. Mothers were interviewed 2 or 3 days after delivery to obtain data on her social and demographic characteristics, use of psychoactive substances, preventive behaviors, as well as prenatal care. Medical records provided data on complications of pregnancy and delivery as well as the child’s health status at birth. The women were asked whether they used cannabis during pregnancy and, if yes, how often they did so. They were also asked about tobacco use and alcohol consumption. The sample included 14,681 women, and 13,545 answered the question about cannabis use during pregnancy. The percentage of cannabis use was assessed by social and demographic characteristics, level of education, employment during pregnancy, and household income. Percentages of preterm birth, spontaneous preterm birth, medically indicated preterm birth, and SGA birth were estimated on the basis of cannabis use. Overall, 156 women (1.2%) reported using cannabis during pregnancy (95% confidence interval, 0.01%–3.0%); 19% did not answer the question about frequency of use, 40% reported using cannabis less than once a month, 26% reported using cannabis 1 to 9 times a month, and 15% reported using cannabis 10 or more times a month. Cannabis use was more common among women younger than 25 years, those with low parity, French women, single women, those with a low level of education, and those with a low monthly income. It was not significantly related to employment status during pregnancy. Cannabis users more frequently used tobacco and alcohol than did nonusers. The preterm birth rates were 10.9% and 5.3% among cannabis users and nonusers, respectively (P < 0.002). The percentages of births at less than 32 weeks were 1.3% and 0.5%, respectively (P < 0.05). The spontaneous preterm birth rate was 6.4% for cannabis users and 2.8% for nonusers (P < 0.004). When examined by frequency of use, the preterm birth rates were 5.3%, 9.9%, and 12.3% among nonusers, women using cannabis less than once a month, and more frequent users, respectively (P < 0.01). The risk for SGA birth differed significantly according to cannabis use, and the mean weight adjusted for gestational age was lower in cannabis users. Among non–tobacco smokers, only gestational age was associated with cannabis use, with a higher percentage of babies born at less than 32 weeks among cannabis users. Among tobacco smokers, the risks for preterm and spontaneous preterm birth were significantly higher among cannabis users. The tobacco-cannabis interaction was not significant for any indicator of pregnancy outcome. In France, it is likely that at least 9900 newborns are exposed to cannabis in utero each year. Efforts should continue to inform women and health care providers about the potential consequences of cannabis use and to encourage women to stop cannabis use before they become pregnant.