Maternal Cannabis Use During Pregnancy and Maternal and Neonatal Adverse Outcomes

Cannabis is a psychoactive substance the availability and use of which, in various forms, has been liberalized in many countries across the world. Cannabis use, including by women of reproductive age, has become increasingly common, with (in some studies) >5% of women using the substance even during pregnancy to self treat nausea, vomiting, stress, anxiety, depression, insomnia, chronic pain, and other conditions. Women who use cannabis during pregnancy are more likely to have a medical or mental health condition; they are commonly unaware that cannabis is associated with pregnancy related risks. These risks arise from effects of cannabis on cannabinoid receptors in the placenta as well as from cannabis constituents that cross the placenta and act on receptors in the developing fetal brain; other mechanisms may also operate. This article examines recent cohort studies and meta-analyses on specific maternal and neonatal adverse outcomes associated with gestational exposure to cannabis. Maternal cannabis use during pregnancy is associated with small to moderately increased risks of gestational hypertension, gestational weight gain less than as well as greater than guidelines, and placental abruption. Maternal cannabis use during pregnancy is also associated with small to moderately increased risks of preterm birth (<36 weeks, <34 weeks, and <32 weeks), small for gestational age, low birth weight, neonatal intensive care unit admission, and fetal death. The risk of some of these adverse outcomes is greater with greater frequency of cannabis use. These adverse outcomes have been identified even in women who do not use other substances during pregnancy. Other adverse outcomes, such as major congenital malformations and neurodevelopmental disorders, are also reported (but are not discussed in this article). For these and other reasons, many professional bodies across the world are already discouraging women from using cannabis during pregnancy. It is important for pregnant women to be educated about cannabis and pregnancy related risks in a shared decision-making process.