PULLMAN, Wash. — A Washington State University (WSU) study suggests that cannabis use by mothers during pregnancy and nursing could disrupt reproductive development in their daughters and granddaughters.
Led by Kanako Hayashi, a professor in WSU’s College of Veterinary Medicine, the research found that mice exposed to cannabis during pregnancy and nursing gave birth to smaller offspring with delayed puberty and irregular reproductive cycles. These effects were strongest in the first generation and diminished in later generations.
“Our study was specifically designed to gain a better understanding of the long-term consequences of cannabis use by pregnant and nursing mothers,” Hayashi said. “While many people think cannabis is safe to use while pregnant or nursing, our data and other studies suggest otherwise.”
The American College of Obstetricians and Gynecologists advises against cannabis use during pregnancy and breastfeeding. Despite this, national surveys show rising use among pregnant people, reaching 25% during the COVID-19 pandemic.
Hayashi’s team exposed female mice to vaporized cannabis extract from the start of pregnancy until weaning. They tracked outcomes across three generations, finding that first-generation litters experienced disrupted development, while the effects were milder in the second generation and disappeared by the third.
Hayashi emphasized the importance of considering how cannabis use during pregnancy could affect future generations, noting, “Cannabis can make people feel relaxed and relieve stress… but it’s important to consider how those choices may affect children and even grandchildren.”
The study did not find evidence of cannabis-induced preterm birth or stillbirth but noted that some women who use cannabis may also consume other substances.
Hayashi’s lab is now exploring cannabis exposure’s effects on male fertility, with early findings suggesting more severe reproductive effects in male offspring.
