Children whose mothers use marijuana during pregnancy are at a greater risk of autism, reveals study
Women who use weed during pregnancy can put their children at a higher risk of autism, according to researchers. They found that children whose mothers reported using marijuana during pregnancy in a study were at greater risk of autism. The analysis reveals that the incidence of autism was 4 per 1,000 person-years among children exposed to cannabis in pregnancy, compared to 2.42 among unexposed children.
Women who are thinking about or currently using cannabis during pregnancy should talk to their healthcare provider to help make an informed choice about what is best for them and their baby, the authors recommend. “In the past, we haven’t had good data on the effect of cannabis on pregnancies. This is one of the largest studies on this topic to date. We hope our findings will help women and their healthcare providers make informed decisions,” writes Dr Daniel Corsi, an epidemiologist at The Ottawa Hospital and BORN Ontario, which is affiliated with the CHEO Research Institute, in the analysis published in Nature Medicine.
About 1 in 20 women in the US reports using marijuana while pregnant. In its guidelines, the US Centers for Disease Control and Prevention (CDC) warns that marijuana use during pregnancy can be harmful to the baby’s health. The chemicals in marijuana, in particular, tetrahydrocannabinol or THC, pass through the mother’s system to the baby and can harm the baby’s development, explains the agency. “Some research shows that using marijuana while you are pregnant can cause health problems in newborns — including low birth weight. Breathing marijuana smoke can also be bad for you and your baby. Marijuana smoke has many of the same chemicals as tobacco smoke and may increase the chances for developmental problems in your baby,” says the CDC.
According to the health experts, some studies suggest that marijuana use during pregnancy may make it hard for the child to pay attention or to learn, and these issues may only become noticeable as the child grows older. “Although more studies are needed to better understand how marijuana may affect you and your baby during pregnancy, it is recommended that pregnant women do not use marijuana. Separate from the direct, chemical effects of marijuana on a baby, use of marijuana may affect a mother’s ability to be able to properly care for her baby,” recommends the CDC.
Recreational marijuana is now legal in Canada, but the research team cautions that it does not mean it is safe for people who are pregnant or breastfeeding. Health Canada and the Society of Obstetricians and Gynaecologists of Canada recommend against these populations using cannabis, and health warnings to this effect appear on marijuana packaging. “Despite these warnings, there is evidence that more people are using cannabis during pregnancy. This is concerning because we know so little about how cannabis affects pregnant women and their babies,” emphasizes Dr Mark Walker, the author of the current study, chief of the Department of Obstetrics, Gynecology and Newborn Care at The Ottawa Hospital, and professor at the University.
For their analysis, the researchers reviewed data from every birth in Ontario between 2007 and 2012, before recreational cannabis was legalized. Of the half-a-million women in the study, about 3,000 or 0.6% reported using marijuana during pregnancy. The team had previously found that cannabis use during pregnancy was linked to an increased risk of preterm birth, and created an animated video to summarize their findings. In that study, they found that women who used cannabis during pregnancy often used other substances including tobacco, alcohol, and opioids.
Considering those findings, the authors specifically looked at 2,200 women who reported using only cannabis during pregnancy, and no other substances in the current analysis. They found that babies born to this group still had an increased risk of autism compared to those who did not use marijuana. The team concludes that marijuana use in pregnancy is linked to a greater risk of autism. The researchers, however, do not know how much cannabis the women were using, how often, at what time during their pregnancy, or how it was consumed. “Parents-to-be should inform themselves of the possible risks (of using marijuana during pregnancy), and we hope studies like ours can help,” says Dr Mark.