Cannabis refers to products derived from the Cannabis sativa plant, containing compounds like tetrahydrocannabinol (THC), responsible for its psychoactive effects. Birth defects are structural abnormalities present at birth. This article explores the scientific understanding of connections between cannabis use during pregnancy and birth defects, along with other developmental concerns.
Current Research on Birth Defects and Cannabis
Research into the direct link between cannabis use during pregnancy and structural birth defects presents several challenges. It is difficult to isolate cannabis effects from other factors like alcohol, tobacco, lifestyle, and varying potency. Increased THC content over time makes older research less comparable. Self-reported use can also introduce bias.
Human observational studies show mixed evidence regarding a firm link between cannabis use and major structural birth defects. A 2023 meta-analysis found inconsistent evidence for a direct association. However, two rare anomalies—Ebstein anomaly (heart) and gastroschisis (abdominal wall)—showed associations in limited data. Conversely, a 2024 meta-analysis indicated a higher risk for various structural birth defects (cardiovascular, gastrointestinal, central nervous system, genitourinary), noting study heterogeneity.
Animal studies contribute to understanding how cannabis might affect fetal development, but findings aren’t always directly applicable to humans due to species differences and higher exposure levels. These studies suggest that THC and other cannabinoids cross the placenta, potentially altering molecular pathways essential for fetal development. Animal models indicate potential for developmental issues, including dysmorphologies and altered neurodevelopment.
Other Potential Fetal Development Impacts
Beyond structural birth defects, cannabis use during pregnancy is associated with other adverse outcomes for fetal growth and neurodevelopment. THC readily crosses the placenta to the developing fetus. This exposure can affect placental function and fetal growth.
Studies have observed associations between prenatal cannabis exposure and reduced birth weight, preterm birth, and smaller head circumference. For instance, infants exposed to cannabis in utero may have lower average birth weights, shorter lengths, and smaller head circumferences. These growth impacts are distinct from structural birth defects but can have significant implications for a newborn’s health.
Neurodevelopmental effects are a concern, with some studies suggesting impacts on attention, memory, problem-solving skills, and behavior in later childhood. THC can interfere with the endocannabinoid system, which plays a role in fetal brain development. While some research points to impaired cognitive functions and behavioral problems, other longitudinal studies have found no significant long-term neurodevelopmental deficits after accounting for other factors.
Medical and Public Health Recommendations
Major medical and public health organizations universally recommend avoiding cannabis use during pregnancy and breastfeeding. Organizations like the American College of Obstetricians and Gynecologists (ACOG), the Centers for Disease Control and Prevention (CDC), and the Surgeon General advise against any cannabis use during these periods. This recommendation extends to all forms: smoking, vaping, edibles, and topical applications.
This guidance stems from potential risks to fetal development, unknown long-term effects, and no evidence that any amount of cannabis is safe during pregnancy. THC, the active compound, passes through the placenta to the fetus and into breast milk. There are no medical indications for cannabis use during pregnancy or breastfeeding.
What to Do and Where to Find Support
Pregnant individuals who have used or are considering cannabis should have an open conversation with their healthcare provider. Healthcare professionals are the best resources for personalized advice and support, providing guidance without judgment. Discussing cannabis use ensures appropriate maternal and fetal care.
Cessation of cannabis use is important for optimal maternal and fetal health. Healthcare providers can offer support and resources, including counseling, treatment programs, or support groups. Individuals planning pregnancy should also consider discontinuing cannabis use beforehand, as early fetal brain development begins before pregnancy is confirmed.