Pre-natal cannabis exposure and its effect on infants

With increased legalization and decriminalization of cannabis in certain regions of the world, as well as a few states in the US, it is really important to know just exactly how cannabis may affect users in multiple areas of their lives. Cannabis is a psychoactive drug that comes from the cannabis plant, mainly containing the cannabinoids THC and CBD. (NIH, 2019) While more recent research has suggested that THC and CBD both have their own benefits and drawbacks, an area that is crucial to examine more closely is the impact of using cannabis while pregnant. 

Cannabis is the world’s third most popular recreational drug behind alcohol and tobacco. (Wu, 2011) In terms of cannabis use among pregnant women, it is estimated that about 3-5% use cannabis in some form during these nine months, making it the most commonly used illicit drug during pregnancy. (Haight, 2021) Because of the frequency in which pregnant women use cannabis, many studies have looked to examine how newborns are affected by prenatal cannabis exposure. While some studies have found no real links between pre-term cannabis exposure and consequential birth outcomes, others have found significant associations of prenatal cannabis use and decreased fetal growth, low birthweight or smaller mean birth weight, decreased gestational period and a few other outcomes. (Haight, 2021)

Some studies have examined the ways in which prenatal exposure to cannabis may affect the cognitive processes of infants. In this area of study, previous research has suggested that prenatally cannabis-exposed children display cognitive deficits, suggesting that marijuana consumption among pregnant women has interfered with the proper maturation of the fetus’ brain. (Wu, 2011) To further examine this, one research team conducted a longitudinal study on a group of women from Pittsburgh who reportedly used alcohol and marijuana while pregnant. The study found that pregnant women who reportedly smoked more than one joint per day during the third trimester of pregnancy had children who had decreased scores on the Bayley Scales of Infant Development at nine months of age. (Wu, 2011) Importantly, this study did mention that lower scores disappeared among children exposed to prenatal cannabis around eighteen months of age. Further, no cognitive deficits were observed during early childhood (ages 1-3 years old). 

Another study looked at birth weight between non-cannabis exposed and cannabis-exposed infants. In a study of 7452 infants (including infants exposed to cannabis only in early pregnancy, infants exposed to cannabis throughout pregnancy, non-exposed and tobacco-exposed infants) birth weight in cannabis exposed infants was 277 g (roughly 0.6 pounds) lower on average compared with those non-exposed to cannabis throughout pregnancy and 156 g (roughly 0.34 pounds) lower for infants exposed to cannabis in just early pregnancy. (Gunn, 2015) Additionally, total head circumference was reduced in cannabis-exposed fetuses compared to tobacco-exposed and non-exposed fetuses, however transcerebellar diameter did not differ, suggesting the brains of cannabis-exposed fetuses are not smaller than non-exposed fetuses. (Gunn, 2015) 

Another concern regarding prenatal cannabis exposure is the risk of preterm birth. In a meta-analysis that examined 27 articles between 1986-2022, there was consistent evidence of an association between prenatal cannabis exposure and preterm birth. (Duko, 2022) Other studies have also suggested that prenatal cannabis exposure may be associated with the development of mental disorders, such as depression, later in life. (Roncero, 2020)

Overall, these findings suggest that there may be some legitimate consequences to using cannabis while pregnant, however, it is possible that some of the risks have been overstated. The majority of studies reported minor differences between cannabis-exposed and cannabis non-exposed groups, which may mean more research needs to be conducted in order to arrive at a more solid understanding of how exactly prenatal cannabis exposure can affect future generations. 


Darshan S. Shah, Emmitt L. Turner, Alyson J. Chroust, Kathryn L. Duvall, David L. Wood & Beth A. Bailey(2022) Marijuana use in opioid exposed pregnancy increases risk of preterm birth, The Journal of Maternal-Fetal & Neonatal Medicine, 35:25, 8456-8461, DOI: 10.1080/14767058.2021.1980532

Duko, B., Dachew, B., Pereira, G., & Alati, R. (n.d.). The effect of prenatal cannabis exposure on offspring preterm birth: A … Wiley Online Library. Retrieved April 17, 2023, from 

Gunn, J. K., Rosales, C. B., Center, K. E., Nuñez, A. V., Gibson, S. J., & Ehiri, J. E. (2015). The effects of prenatal cannabis exposure on fetal development and pregnancy outcomes: a protocol. BMJ open, 5(3), e007227.

Haight, S. C., Gelder, M. M. H. J. van, Shiono, P. H., Coleman-Cowger, V. H., Fergusson, D. M., Chabarria, K. C., Fried, P. A., Massey, S. H., Howard, D. S., Crume, T. L., Bayrampour, H., Ebrahim, S. H., & Marroun, H. E. (2021). Prenatal cannabis use and infant birth outcomes in the pregnancy risk assessment monitoring system. The Journal of Pediatrics. 

Roncero, C., Valriberas-Herrero, I., Mezzatesta-Gava, M. et al. Cannabis use during pregnancy and its relationship with fetal developmental outcomes and psychiatric disorders. A systematic review. Reprod Health 17, 25 (2020).

U.S. Department of Health and Human Services. (2019). Cannabis (marijuana) and cannabinoids: What you need to know. National Center for Complementary and Integrative Health. 

Wu, C. S., Jew, C. P., & Lu, H. C. (2011). Lasting impacts of prenatal cannabis exposure and the role of endogenous cannabinoids in the developing brain. Future neurology, 6(4), 459–480.

2 thoughts on “Pre-natal cannabis exposure and its effect on infants

  1. Hi Mason. This was a really interesting post! It was really informative to learn about cannabis and pregnancy especially because the effects of alcohol and tobacco are the most publicized. You had a good variety of studies cited and made some interesting connections between them. I wonder if there has been any research done on how the different ways of using cannabis affect pregnancy. I also think it could have been good to wrap up by pointing to some specific studies that haven’t found any evidence.


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