Cannabis Use in Pregnancy Could Harm Development of Fetal Male Sex Organs, Study Says

Marijuana plants grow at the Green Pearl Organics marijuana dispensary in Desert Hot Springs, Calif., on Jan. 1, 2018. Robyn Beck/AFP via Getty Images

The use of cannabis during pregnancy could adversely affect the development of a fetus’ brain and likely hinders the healthy growth of the testes in male babies, according to recent studies.

Women sometimes use cannabis or CBD, a nonpsychoactive component of marijuana, during pregnancy to help deal with anxiety and nausea. In a study published July 11 in Molecular Psychiatry, researchers at the University of Colorado Anschutz Medical Campus investigated how CBD affects a fetus’ brain development by using mice for test purposes.

Pregnant mice were given CBD during their pregnancy through birth.

Researchers found that fetal exposure to CBD reduced the ability of the mice’s prefrontal cortex—a region in the brain crucial for learning—to be readily roused into action.

Female offspring were found to have suffered cognitive impairments, with a high dose of CBD affecting problem-solving skills. Among male offspring, higher pain sensitivity was observed.

“This study is important to help clinicians and pregnant patients know that consuming CBD during pregnancy may have some effect on the brain development of offspring,” said Emily Bates, an associate professor at the University of Colorado School of Medicine and lead author of the study, in a statement.

“It’s important now more than ever because CBD recently became federally legal and is available at grocery stores and gas stations. We need clinicians to start asking about CBD consumption at prenatal visits and educate the public about potential risks during pregnancy.”

Effects on Male Testes

In another study published in the National Library of Medicine on July 11, researchers found that cannabis consumption can result in harmful effects on the development of male testes in the fetus.

The testes are the two egg-shaped glands inside the male scrotum that produces sperm and male hormones. In a male fetus, it is the endocrine function of the testes to orchestrate the masculinization of several organs.

The study authors emphasized that cannabis consumption by pregnant women has risen worldwide over the past few decades and that numerous countries are debating the drug’s legalization for its recreational and therapeutic purposes.

“An understanding of the potential adverse effects of exposures to cannabis components on the establishment of the male reproductive functions during development is urgently needed,” the researchers said. “Our study highlights potential deleterious effects of cannabinoids on the developing testis and paves the way for further deciphering of the impact of cannabinoids at the molecular and cellular levels in the fetus.”

In another study published in 2022 in Fertility and Sterility (pdf), long-term cannabis use was found to significantly impact male fertility.

A selection of adult male nonhuman primates were exposed to edible THC over a period of time with increased dosage in alignment with the animals’ sperm development cycle. The amount of THC was increased subsequently to a level of a heavy medical marijuana dose within humans, before the primates’ semen was collected for research.

“Our analysis of the collected samples found that THC use was associated with significant adverse impacts to the animals’ reproductive hormones, including decreased levels of testosterone and severe testicular shrinkage. Specifically, we observed a greater than 50% decrease in testicular size,” said the study’s senior author Dr. Jamie Lo, associate professor of obstetrics and gynecology at the Oregon Health and Science University School of Medicine.

“Unfortunately, these effects appeared to worsen as the THC dose was increased, suggesting a possible dose-dependent effect,” she said.

Federal Warnings, Low Weight in Babies

Various federal agencies have warned against the intake of marijuana by pregnant women.

According to the Substance Abuse and Mental Health Services Administration (SAMHSA), “a growing number of pregnant women view it as a safe, natural way to treat nausea and vomiting, or ‘morning sickness.' But marijuana use during pregnancy is not safe and comes with serious, potentially deadly risks.”

“Avoiding marijuana during pregnancy and breastfeeding can give your baby a healthier start in life,” the agency advised. “No amount of marijuana has been proven safe to use during pregnancy or while breastfeeding.”

Marijuana contains nearly 500 chemicals, including mind-altering compounds that can pass through a woman’s placenta and enter the unborn baby.

Citing multiple studies, SAMHSA states that marijuana use during pregnancy can result in fetal growth restriction, low birth weight, preterm birth, and long-term brain development issues that can affect memory, learning, and behavior.

Marijuana use during breastfeeding is risky as some of the chemicals can pass through the milk to the baby. According to the U.S. Centers for Disease Control and Prevention (CDC), the THC present in marijuana is stored in body fat and released slowly over time.

This means that the baby can still be exposed to such chemicals even after the mother has stopped using cannabis. The CDC encourages pregnant women to “avoid all marijuana use.”

Infant weight and head circumference have been found to be affected due to marijuana use among pregnant women. A May 16 study published in “Frontiers in Pediatrics” found that there was a “significant decrease” in the weight of newborns born to women who used marijuana during the first trimester of pregnancy. The weight of such newborns was lower by an average of 154 grams.

If women continued marijuana use throughout gestation, their newborns’ weights were lower by an average of 185 grams.

Researchers also found “significant deficits” in head circumference. Infants born to women who used marijuana in the first trimester had a head circumference deficit of 0.47 centimeters, while those born to women who used marijuana throughout pregnancy had a deficit of 0.79 centimeters.

The study authors said low birth weight and head circumference have been associated with multiple neurological and psychological issues as well as health complications in childhood and adulthood.