Hidden Consequences: How Maternal Cannabis Use Can Alter a Baby's Genes

New research has revealed a troubling link between maternal cannabis use and genetic changes in babies, shedding light on a previously hidden danger of prenatal exposure. The study, conducted by researchers at Te Whare Wānanga o Waitaha | University of Canterbury (UC), has provided the first clear evidence that using cannabis during pregnancy can cause molecular alterations in a child’s genes—changes that may have long-term effects on brain development.

Dr. Amy Osborne, Senior Lecturer at the UC School of Biological Sciences, led the groundbreaking study, which was published in Molecular Psychiatry. “We’ve long known that cannabis use during pregnancy is associated with impacts on childhood brain development and cognitive function,” Dr. Osborne explains. “However, past studies struggled to definitively link prenatal cannabis exposure with the adverse neurodevelopmental outcomes we’ve observed.”

This new study changes that narrative. For the first time, researchers identified molecular changes in the DNA of children whose mothers used cannabis while pregnant. These changes, which affect genes involved in neurodevelopment, could explain the developmental issues and cognitive impairments seen in children exposed to cannabis in utero.

Cannabis is now the most commonly used drug, aside from alcohol and tobacco, among pregnant women in the United States—a trend that has been rising since the COVID-19 pandemic. This is cause for concern, Dr. Osborne warns, as many expectant mothers turn to cannabis or cannabis-containing products to alleviate pregnancy symptoms such as nausea or anxiety, unaware of the potential risks.

"With the wider availability of cannabis products in many countries, including the U.S. and potentially in New Zealand in the near future, cannabis use during pregnancy is on the rise," Dr. Osborne says. "However, the harm of this practice, particularly its impact on developing babies, is not well understood by the public."

The research, a collaboration between UC and the University of Oxford, utilized genomic data from two large-scale longitudinal studies: the Avon Longitudinal Study of Parents and Children in the UK and the Christchurch Health and Development Study in New Zealand. By analyzing DNA samples from individuals at birth and at key stages of their life—ages 7, 15-17, and 27—the researchers were able to identify a clear molecular signature linked to prenatal cannabis exposure (PCE).

Dr. Osborne describes the findings as both novel and alarming. “We found genome-wide significant DNA changes in the children of mothers who used cannabis during pregnancy. These molecular alterations directly affect genes associated with brain development and neurodevelopmental diseases,” she says. “This is a key discovery because it suggests a biological mechanism behind the cognitive and developmental issues observed in exposed children.”

According to the study, these changes in DNA could have lifelong consequences. They not only affect the brain's developmental processes but may also increase susceptibility to neurodevelopmental disorders such as ADHD, autism, or learning disabilities. As Dr. Osborne notes, this research provides the strongest evidence to date that maternal cannabis use has a lasting impact on the genetic makeup of offspring.

The findings of the study underscore the serious risks that cannabis use during pregnancy poses to the long-term health of children. These genetic alterations are not superficial—they affect the very building blocks of brain development, potentially impairing cognitive abilities and increasing vulnerability to mental health disorders later in life.

"We’ve essentially uncovered a molecular link that explains why we see higher rates of neurodevelopmental challenges in children exposed to cannabis in the womb," says Dr. Osborne. "It’s no longer just a correlation—we’re seeing real, measurable changes in their DNA."

Dr. Osborne hopes that this research will prompt more large-scale studies into prenatal cannabis exposure and its effects on children. “We need to investigate these findings further with larger cohorts to better understand the full scope of the impact. Only then can we offer clearer guidance to pregnant women,” she says.

As cannabis becomes more widely available, the need for better public health messaging grows. Many pregnant women are still unaware of the potential dangers posed by cannabis use, partly due to the perception that it is a natural, harmless substance. This misconception, Osborne argues, could lead to lasting harm for their children.

“Without more research and clear public health campaigns, the potential risk to children will not only remain but likely increase as cannabis use becomes more normalized,” she adds.

The study’s findings are a sobering reminder of the hidden consequences that cannabis use during pregnancy can have. While cannabis may offer relief from pregnancy symptoms, the long-term cost to the child’s health and development is a risk that expecting mothers need to be more aware of.

Do you think pregnant women should be more cautious about using cannabis?