Prenatal Exposure

This page reviews existing peer-reviewed clinical and public health research regarding marijuana use during pregnancy and its effects on pregnancy outcomes, neonatal characteristics, and cognitive and developmental performance of offspring at various stages throughout childhood and adolescence.  (For a comprehensive, objective analysis of the subtle impact of prenatal cannabis exposure, see Dr. Peter A. Fried’s 2002 article, “The Consequences of Marijuana Use During Pregnancy: A Review of the Human Literature.“)  The majority of this literature reports findings from two long-term ongoing cohort studies in North America: the Ottawa Prenatal Prospective Study (OPPS), which began in 1978, and the Maternal Health Practices and Child Development Project (MHPCD) in Pittsburgh, which began in 1982. This analysis also includes studies carried out since 1988 with additional cohorts of pregnant mothers from the United Kingdom, Brazil, Denmark, Jamaica, and the U.S.

Several factors complicate the task of assessing the clinical impact of prenatal marijuana exposure. The relationship between prenatal marijuana exposure and outcome measures such as low birth weight, gestational age, child hyperactivity, depression, school performance, IQ, and behavioral problems is potentially confounded by many demographic factors, such as socioeconomic status, race, maternal age, maternal education, prenatal care, tobacco exposure, alcohol exposure, polydrug exposure, home environment, school attendance, and more. While some researchers attempted to control for these and other factors, others did not include confounding factors in their analyses. Studies varied in their classification of frequency of use (i.e., amount of daily joints, or ADJ, versus “light” or “heavy” marijuana use) and in their reliance on self-reports or on confirmed toxicology results. Though pregnancy outcomes can be measured using fairly straightforward methods (birth weight, birth length, head circumference, gestational age), a wide variety of instruments were used to assess cognitive performance.

Finally, most studies performed in the United States (including OPPS and MHPCD) are at least partially funded by the National Institute on Drug Abuse (NIDA), a federal government agency that has a policy of funding only research focused on the negative consequences of marijuana use. NIDA has refused to fund or supply some FDA-approved research protocols proposing to study the benefits of marijuana, effectively stifling scientific inquiry and manipulating the range of possible findings in this field.


Studies on Pregnancy Outcomes and Neonatal Period

  • Balle, J., Olofsson, M.J., & Hilden, J. (1999). Cannabis and pregnancy. Danish Medical Journal, 161(36), 5024-28.


Studies on Cognitive & Behavioral Outcomes

Last updated: November 6, 2014 at 16:29 pm


Social Widgets powered by