A sweeping review of global evidence reveals that cannabis use during pregnancy may lead to serious consequences for fetal development and long-term child health, prompting renewed warnings from health experts.
Key Points at a Glance
- THC exposure in pregnancy alters fetal gene expression linked to neurodevelopmental disorders.
- Studies show reduced fetal lung volume after prenatal cannabis use, persisting into infancy.
- Data from 21 million pregnancies links cannabis to higher risks of preterm birth and low birth weight.
- Combined cannabis and nicotine use during pregnancy quadruples the risk of infant death.
- Experts urge pregnant individuals to avoid cannabis and seek safer alternatives for symptom relief.
When it comes to pregnancy, every choice matters. Yet a growing body of research suggests that one increasingly common decision—using cannabis—may carry risks far more serious than many expect. A recent evidence review by Oregon Health & Science University (OHSU) is sounding the alarm: prenatal cannabis use could compromise fetal development in ways that have lifelong consequences.
The findings are based on an analysis of multiple large-scale and preclinical studies, with a focus on tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis. The implications are sobering. According to the review, THC can disrupt the delicate developmental processes taking place in the womb, affecting everything from genetic expression to organ development.
One of the most striking revelations comes from a 2023 preclinical study involving non-human primates. The research found that THC exposure during pregnancy can modify the placental and fetal epigenome—chemical modifications that influence gene activity without altering DNA sequences. These changes mirror those seen in neurodevelopmental conditions such as autism, suggesting a possible link between prenatal cannabis exposure and later cognitive or behavioral disorders.
But the neurological risks are only part of the picture. In early 2025, OHSU researchers published results showing that THC edibles consumed during pregnancy significantly reduced fetal lung volume. This structural change, which persisted into infancy, raises red flags about future respiratory health. Babies born with smaller lung capacity may face a higher likelihood of developing conditions such as asthma or chronic bronchitis.
The dangers aren’t confined to small studies. A massive systematic review encompassing over 21 million pregnancies worldwide revealed that cannabis use is associated with increased risks of preterm birth, low birth weight, and infants being born small for their gestational age. These outcomes not only heighten the chance of complications during delivery but can also impact a child’s physical and cognitive development well into adulthood.
Even more alarming is the discovery of compounding effects when cannabis is used in combination with other substances. A 2024 study found that when cannabis and nicotine are both used during pregnancy, the risk of infant mortality increases fourfold. Even using either substance independently was linked to negative birth outcomes, underscoring the compounded vulnerabilities of the developing fetus.
Despite these risks, cannabis is still often perceived as a relatively harmless or even natural remedy—particularly for common pregnancy symptoms like nausea, anxiety, and insomnia. With its growing legalization and availability, some individuals may turn to THC as a substitute for prescription medications. But health professionals caution against this approach.
“The perception of cannabis as a safe, organic solution is not supported by the evidence,” researchers from OHSU stress. “Our review makes it clear: cannabis use during pregnancy is not without consequence.”
The American College of Obstetricians and Gynecologists already advises against the use of marijuana during pregnancy and lactation. This latest synthesis of data strengthens that position and highlights an urgent need for better public health messaging and clinical support. Pregnant individuals struggling with nausea or sleep disruption should consult their healthcare providers about evidence-based, safer alternatives.
As the science continues to evolve, the takeaway is becoming increasingly clear: what may feel like a benign decision today could influence a child’s health for years to come. Avoiding cannabis use during pregnancy isn’t about fear—it’s about protection, prevention, and making informed choices for the next generation.
