Cannabis use during pregnancy has become increasingly prevalent, especially with expanding legalization. Many pregnant individuals mistakenly perceive cannabis as a natural remedy for symptoms like nausea or anxiety. Understanding the potential consequences of prenatal exposure requires reviewing scientific evidence and the consensus from major medical bodies. This article examines the biological mechanisms and measurable outcomes associated with cannabis use during this sensitive period.
Current Medical Guidance on Use During Pregnancy
The consensus among major health organizations is clear: no amount of cannabis use is considered safe during pregnancy or while breastfeeding. The American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) strongly advise against its use during preconception, pregnancy, and lactation. This recommendation stems from the lack of safety data and the known ability of the substance’s active compounds to cross the placenta and affect the developing fetus.
The guidance also extends to products used for medical purposes, as no standardized dose or formulation has been studied or approved for use in pregnancy. Healthcare providers are urged to counsel patients about the potential adverse health consequences of continued use. These organizations advocate for screening and providing support to help patients discontinue use, focusing on the health of both the mother and the child.
How Cannabis Chemicals Affect Fetal Development
The primary concern lies with delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis. THC is highly lipid-soluble, allowing it to readily cross the placental barrier and enter the fetal bloodstream and brain. Once in the fetal system, THC interacts with the endocannabinoid system (ECS), a regulatory network active from the earliest stages of embryonic development.
The fetal ECS guides fundamental processes of neurodevelopment, including the proliferation, migration, and differentiation of neurons. Introducing exogenous THC, which mimics natural cannabinoids, disrupts this precise signaling pathway. This interference can alter neuronal connectivity and the formation of synapses, disturbing the developing brain’s “hardwiring.” Furthermore, smoking cannabis exposes the fetus to carbon monoxide and other combustion toxins, which compromise oxygen delivery and fetal growth.
Immediate Risks to the Newborn
Exposure to cannabis in utero is consistently associated with several adverse outcomes measurable at birth or shortly thereafter. The most frequently reported physical consequence is restricted fetal growth, leading to a higher risk of low birth weight (LBW). LBW is defined as a birth weight less than 2,500 grams (about 5 pounds, 8 ounces).
Prenatal cannabis exposure also increases the likelihood of the infant being born small for gestational age (SGA), meaning the baby is smaller than expected for the number of weeks of pregnancy completed. Maternal cannabis use is also linked to an increased risk of preterm birth (before 37 weeks of gestation). These factors often necessitate closer monitoring and lead to an increased rate of admission to the Neonatal Intensive Care Unit (NICU). A smaller head circumference, indicating restricted brain growth, has also been observed in children with heavy prenatal exposure.
Long-Term Developmental and Behavioral Outcomes
The impact of prenatal cannabis exposure extends beyond the neonatal period, manifesting as subtle but enduring effects on neurodevelopment. Children exposed prenatally show deficits in cognitive functions, particularly those related to higher-order thinking. These deficits often involve impaired memory, decreased attention span, and difficulties with executive functions, such as planning and impulse control.
Behavioral problems are another consistent finding in longitudinal studies. Issues such as hyperactivity, increased aggression, and impulsivity persist into middle childhood and adolescence. Later, adolescents with a history of prenatal exposure show an elevated risk for mental health issues, including depressive symptoms and vulnerability to psychotic-like symptoms. Researchers face challenges isolating these effects because cannabis use during pregnancy is often accompanied by other factors, such as tobacco or alcohol use, which also influence developmental outcomes.