The Dangers of Using Marijuana During Pregnancy

With eight states and the District of Columbia legalizing marijuana for recreational use, the drug is being viewed as increasingly harmless, even among pregnant women.  In fact, according to the authors of a 2015 study published in Frontiers in Neuroscience, pregnant women use marijuana more than any other illegal drug.  While marijuana use is common during pregnancy, that does not mean it is safe.  Here, learn about the potential negative effects of using marijuana while pregnant.

Risk of Low Birth Weight

The research has shown that babies born to marijuana-using mothers are at risk of being underweight at birth.  Researchers for a 2009 edition of the Journal of the American Academy of Child & Adolescent Psychiatry found that mothers who used marijuana during pregnancy gave birth to babies with lower birthweights; the babies of marijuana-using mothers experienced growth restriction during the middle and late stages of pregnancy.

A 2010 study in Clinical Chemistry found similar results.  Babies in the study weighed less, had smaller head circumferences, and were shorter in length when mothers used marijuana during pregnancy. 

Being born at a low weight can lead to health complications and longer hospital stays for babies exposed to marijuana.  A 2016 review in BMJ Open analyzed the results of 24 studies and found that marijuana exposure during the prenatal period was linked to low birthweight and placement in the neonatal intensive care unit. A 2012 study in Pediatric Research drew a similar conclusion, finding that marijuana exposure increased the odds of infants being born at a low birth weight, being premature, and requiring admission to the intensive care unit.

Developmental Effects

In addition to increasing the odds of low birth weight, prenatal marijuana exposure can have a lasting impact on a child’s development.  Scientists investigating for a 2008 publication of the Journal of the American Academy of Child & Adolescent Psychiatry found that children of mothers who used marijuana heavily during the first trimester of pregnancy had lower scores on a verbal reasoning test at age 6.  Second-trimester marijuana use was linked to deficits in short-term memory, and use during the third trimester was associated with a lower IQ score.

The impact of marijuana exposure on cognitive development can, unfortunately, extend into adolescence. A 2012 study in Neurotoxicology and Teratology found that 14-year-old children who were exposed to marijuana prenatally scored lower on an academic achievement test. Lower scores among marijuana-exposed children were explained by the effects of marijuana on intelligence at the age of 6 and on depression and inattention at age 10.

Marijuana might impact intelligence by initiating changes in fetal brain development.  In 2015, researchers for Frontiers in Human Neuroscience analyzed the brain activity of infants between 2 and 6 weeks of age.  They found that those exposed to marijuana during gestation had less connectivity in the brain regions involved with attention, motor skills, and language.

Emotional and Behavioral Functioning

Marijuana exposure can have an impact on children’s behaviors from a young age.  A 2011 study in Drug and Alcohol Dependence found that girls who were exposed to marijuana prenatally were more likely to be aggressive at 18 months of age. Interestingly, the same effect was not seen among boys.

Again, the effects of marijuana can extend beyond early childhood.  Researchers for a 2011 edition of Neurotoxicology and Teratology discovered that heavy marijuana use during pregnancy was associated with delinquency among 14-year-old children.  This effect was due to depression and attention issues linked with marijuana exposure.

The impact of prenatal marijuana exposure can sometimes be severe.  In 2009, a study in The British Journal of Psychiatry found that at age 12, children whose mothers used marijuana during pregnancy were more likely to experience symptoms of psychosis.

Development of Addiction

Beyond the negative impact on emotions and development, a mother’s use of marijuana during pregnancy can make her children more susceptible to drug addiction. For instance, results of a 2015 study in Neurotoxicology and Teratology found that 22-year-old subjects whose mothers used marijuana during pregnancy were more likely to use marijuana themselves.   Researchers for a 2011 publication of Biological Psychiatry found that fetuses exposed to marijuana experienced alterations in their dopamine receptors, which could increase their vulnerability to addiction.

With marijuana exposure being linked to addiction and a myriad of other consequences for children whose mothers use during pregnancy, it appears that this drug is far from being harmless for the developing fetus.  Furthermore, the consequences of early marijuana exposure can extend into adolescence and adulthood.  It is therefore vital that medical practitioners and social service personnel be prepared to educate women about the dangers of using marijuana during pregnancy.