Cannabis Use in Pregnancy Linked to Preterm Birth

American Psychiatric Association

Fri, Nov 18, 2022

Using cannabis while pregnant may raise the risk of preterm birth, a study in Addiction has found.

“The findings further support the message provided by the American College of Obstetricians and Gynecologists that pregnant mothers should be encouraged to avoid cannabis use during [the] prenatal period,” wrote Bereket Duko, Ph.D., of Curtin University in Australia and colleagues.

The researchers analyzed data from 27 studies that measured cannabis use during pregnancy and were published between 1986 and 2022. Each study had between 304 and 4.83 million participants who had live births. Preterm birth was defined as a live birth before the pregnant person completed 37 weeks of gestation.

Participants who used cannabis during pregnancy were 35% more likely to have a preterm birth. The results were similar after the researchers adjusted for the participants’ use of tobacco, alcohol, and other drugs during pregnancy; gestational diabetes; hypertension; household income; and previous preterm birth.

Duko and colleagues offered several possible causes for the increased risk, noting that several compounds in cannabis can cross the placenta, including delta-9-tetrahydrocannabinol (THC) and cannabidiol.

“These chemicals can result in impaired placenta development and insufficient blood circulation,” they wrote. “Insufficient placental blood circulation may result in fetal growth restriction and development. This, in turn, has been associated with spontaneous preterm birth.”

The researchers added that the increased risk may be because of confounding by alcohol, tobacco, or other drug use during pregnancy.

They concluded that the findings warrant public health messages to avoid cannabis exposure, particularly during pregnancy.