Is it safe to use THC during pregnancy or lactation?

Data collected in the United States from 2016 to 2017 found that around 7% of pregnant women reported using cannabis during pregnancy.^[1] While potentially helpful for nausea and vomiting, THC is not recommended during pregnancy for several reasons.

The cannabinoid receptor 1 (CB1) receptors that THC exerts its actions through are found in the fetus as early as the first trimester and play an important role in the development of the nervous system. This, paired with the knowledge that THC crosses the placenta, raises a legitimate concern about the effects early exposure to THC might have on the developing fetus.^[2]

Observational research suggests that exposure to cannabis during pregnancy may be associated with an increased risk of low birth weight, preterm birth (<37 weeks gestation), small for gestational age diagnosis, and admission to the neonatal intensive care unit (NICU).^[3][2] Whether cannabis exposure during pregnancy affects cognitive processes into childhood is poorly researched. However, some preliminary research suggests it may be associated with impairments in attention and a higher likelihood of aggressive and hyperactive behaviors.^[2]

Regarding lactation, THC has been found to concentrate in breast milk, meaning levels of THC in breast milk can accumulate and exceed plasma levels in people who use cannabis regularly.^[4] Regular use of THC may also affect the composition of breast milk.^[5] Still, how THC exposure through breast milk affects an infant in both the short-term and the long-term is poorly researched.^[6]