Since 2009, an increasing number of pregnant women in California have been found to smoke cannabis despite unknown dangers the illicit drug could cause to their unborn child.

A new study included more than 300,000 pregnant women receiving care from Kaiser Permanente Northern California, one of the state's largest healthcare systems. The sample group was specifically comprised of females who were approximately two months pregnant and aged 12 years up. They were asked to undergo a toxicology test two weeks after completing a questionnaire.

More Pregnant Women Use Cannabis Each Year

Based on data gathered over an 8-year period, the number of pregnant women smoking in California has increased from 4.2 percent in 2009 to 7.1 percent in 2016 with an annual growth rate of 1.075 percent.

Expecting mothers age below 18 as well as those who are between ages 18 and 24 recorded the highest increase over the duration of the study. Data gathered in 2016 alone showed that almost 25 percent of expecting teenagers and one out of five pregnant women age 18 to 24 had been using cannabis.

"That was not surprising, necessarily, but definitely concerning," says co-author Kelly C. Young-Wolff through a report. She continued that data is expected to be higher in California as the state is the first to legalize cannabis in the 1990s and that results may serve as a preview of what could happen to other states.

Moreover, the same report suggests that the number of people smoking weed in California, pregnant or not, may have increased and that using cannabis has become more acceptable in the state.

Physicians Express Concern Over Unknown Effects Of Smoking Marijuana During Pregnancy

For a national committee of physicians, the trends revealed by the California study appeared worrisome. The American Congress of Obstetricians and Gynecologists updated a document that represents the organization's opinion on pressing matters titled the ACOG Committee Opinion. In October, more scientific information was added as well as a statement explicitly discouraging the use of marijuana among females while pregnant or breastfeeding.

Among the research included in the document is one involving pregnant laboratory animals that were exposed to the illicit drug. The ACOG states that results of such experiment show that marijuana exposure could potentially hinder an unborn baby's brain development and function and that it could also increase the child's tendency to abuse drugs later on life.

The committee went on to cite more studies that claim children who were exposed to cannabis while still in their mothers' wombs performed poorly in school, exhibited shorter attention span, and failed visual tests.