The survey results were among 276,991 pregnant women (representing 367,403 pregnancies) in Northern California over 9 years. From 2009 to 2017, the adjusted prevalence of self-reported cannabis use in the year before pregnancy increased from 6.8% to 12.5%, and the adjusted prevalence of self-reported cannabis use during pregnancy increased from 1.9% to 3.4% (rates were adjusted for demographics). Annual rates of change in self-reported daily, weekly, and monthly-or-less cannabis use increased significantly, though daily use increased most rapidly.
Among women who self-reported cannabis use during the year before pregnancy, the proportion who were daily users increased from 17% to 25%, and weekly users increased from 20% to 22%, while monthly-or-less users decreased from 63% to 53% during the study period. Similarly, among women who self-reported cannabis use during pregnancy, the proportion who were daily users increased from 15% to 21%, and weekly users from 25% to 27%, while monthly users decreased from 60% to 52%.
It could be even worse now, following legalization of cannabis for recreational use in California in 2018.
There are confounders so the real results could be higher or lower. The data come from women's initial prenatal visits at Kaiser Permanente in Northern California, which usually take place at around 8 weeks gestation, and investigators were unable to differentiate whether self-reported cannabis use during pregnancy occurred before or after women were aware that they were pregnant.
It is not a morning sickness drug, it is a drug with the added risks of cigarettes
Some claim to believe it might help with morning sickness, the authors noted. A paper in JAMA Internal Medicine in 2018 showed women with severe nausea and vomiting in pregnancy were nearly 4 times more likely to use cannabis during the first trimester of pregnancy and since cannabis is now a legal supplement, unethical marketers often suggest a variety of benefits, but it is actually a depressant, a hallucinogen and a stimulant with the added health risks of cigarettes.
Exposure to marijuana in pregnancy is associated with having low-birthweight babies, and the American College of Obstetricians and Gynecologists recommends women who are pregnant or contemplating pregnancy discontinue cannabis use because of concerns about impaired neurodevelopment and exposure to the adverse effects of smoking.