Marijuana Use During Pregnancy Poses Significant Risk of Preterm Birth

Yet another risk factor associated with marijuana use during pregnancy emerges.

Marijuana in Pregnancy Anton Watman/Shutterstock
Recent research has identified a significant risk of preterm birth associated with marijuana use during pregnancy. 

The researchers looked at several lifestyle factors (think smoking, age, weight, socioeconomic status) and their effects on pregnancy outcomes. Here's one major finding that emerged from a study of over 5,500 pregnant women in Australia, New Zealand, Ireland and the United Kingdom: Continued marijuana use during pregnancy created a five-fold increase in the risk of preterm birth. This is incredibly alarming—especially because marijuana has likely accounted for many preterm birth outcomes that could have been prevented.

"Our results suggest that more than 6 percent of pre-term births could have been prevented if women did not use marijuana during pregnancy, irrespective of other risk factors," lead author Professor Claire Roberts from the University's Robinson Research Institute said. "In the Australian participating center, which has a higher proportion of pregnant marijuana users, almost 12 percent of pre-term births could have been prevented."

We have reported on issues that can arise from marijuana use during pregnancy but according to a release for the study, this is the first time the effect on preterm birth has been identified.

"This is the first time that continued marijuana use in pregnancy has been independently linked to pre-term birth. Based on our findings, we consider marijuana to be a major public health concern for pregnant women and their babies," Professor Roberts said.

The study found that of the 236 pre-term births observed, women who continued to use marijuana after 20 weeks gestation had shorter gestation periods (an average of just 30 weeks) than women who did not use marijuana at the same point—and 36 percent of the marijuana users surveyed delivered at less than 28 weeks gestation

Professor Roberts urged women woldwide to consider these results.

"In the United States, 23 states have now legalized marijuana in some form, either for medicinal or recreational use. Canada's government has also promised to decriminalize marijuana for recreational use. Such widespread legalization of marijuana raises concerns about its safety for pregnant women," she said. "Anecdotally, we know that some women are using marijuana to reduce nausea in pregnancy, even though there is no medical evidence to support this. Our study was unable to determine whether there is a 'safe' time prior to 20 weeks' gestation to give up marijuana. Therefore, we recommend total abstinence from marijuana during pregnancy."

Related: Your Premature Birth Risk by U.S. State