Smoking during pregnancy is a major public health problem that can cause adverse health outcomes and neurodevelopmental abnormalities in the maternal offspring. Dr. Solja Niemelä and colleagues found that nicotine exposure during pregnancy significantly increased the risk of schizophrenia in offspring. The findings were published online May 24 in the American Journal of Psychiatry. The study was based on a population-based, nested case-control study of all live births in Finland during 1983-1998. Researchers obtained information on maternal offspring with schizophrenia from the National Information Registry, which included 977 subjects, with each case matched 1:1 by date of birth, sex and residence. At the same time, serum specimens from the corresponding maternal early and mid-pregnancy periods from the National Biosample Inventory file were extracted, and maternal serum cotinine (the main primary metabolite of nicotine) levels were measured prospectively using a quantitative immunoassay. The results of the study showed that maternal cotinine levels (measured as a continuous variable) were positively associated with an increased risk ratio for schizophrenia in offspring (OR=3.41, 95% CI, 1.86-6.24). Heavy maternal nicotine exposure was associated with a 38% increased risk of schizophrenia in offspring. This was independent of maternal age, maternal or parental history of mental illness, socioeconomic status, and other covariates. Also, the study lacked clear evidence that gestational weight moderated the association. The researchers noted that the study is the first to examine the association between schizophrenia and maternal smoking biomarkers. The findings clearly indicate that smoking during pregnancy is significantly associated with the risk of schizophrenia in the offspring. The researchers emphasize that if the results of this study are confirmed by replication, controlling smoking during pregnancy may reduce the risk of schizophrenia in offspring.