Fraser Horton
Fraser Horton
Last Updated on January 20, 2021

The results of a United States study done between 2002-2017 show that marijuana use in pregnant women has increased dramatically. While some women use cannabis as a way to reduce morning sickness in the first trimester, neither the Food and Drug Administration (FDA) nor healthcare providers condone the use of marijuana while pregnant or breastfeeding. 

As you may probably know if you’ve been with us for a while, the cannabis plant contains a wide array of cannabinoids like tetrahydrocannabinol (THC), cannabidiol (CBD), and others, but also terpenes and other chemical compounds. Though cannabis use is known to aid patients who use it as treatment for chronic pain, depression, or anxiety, when pregnant women consume marijuana, it may result in negative effects on the baby’s development.

In order to find out how long cannabis stays in the placenta, and also what effects cannabis use may have on the offspring, read on.

The Effects of Marijuana on the Baby’s System

A study done by the National Institute on Drug Abuse shows that smoking weed can be harmful to the development of the baby. For the sake of obtaining conclusions for their study, scientists compared neonatal growth outcomes in both cannabis-exposed and unexposed babies and the results were very different. 

The study showed that cannabis exposure in babies had potential negative defects including:

  • Low birth weight;
  • Reductions in gestational age;
  • Small head circumference.

While these results might not be related only to cannabis, it’s best to be safe than sorry. Another study done in 2014 by the University of Utah School of Medicine, concluded that “illicit drugs were associated with a 2 to 3-fold increase in stillbirth risk.” The study also found that “prenatal cannabis exposure influences brain development and can have long-lasting impacts on cognitive functions.”

How Long Does Marijuana Stay in the Placenta

With the knowledge of the implications that come with consuming marijuana, you might want to think twice before you reach for a joint while pregnant. But what if you didn’t know you were pregnant at the time and you rolled one with your friends? Will it show up on a drug test at the hospital?

Generally, hospitals don’t go around drug testing all pregnant women before they give birth, but if your doctor suspects that you’ve been using illicit drugs, he may ask you to do a blood test or urinalysis. If it turns out positive, there’s a big chance that your baby will get tested for cannabis exposure after birth.

While in utero, babies receive all the nutrients they need from the umbilical cord, meaning that your baby takes in everything you have consumed. If the mother has consumed cannabis while pregnant, cannabis metabolites will be transferred to the placenta. Provided the mother is suspected of substance use, tests on the meconium and the umbilical cord might be done after birth.

Testing the Meconium and the Umbilical Cord Tissue

Meconium begins to form between the 12-16 week of gestation and it’s essentially your baby’s first bowel movement that gets released after birth. It’s composed of materials ingested in utero like amniotic fluid, mucus, intestinal epithelial cells, lanugo, and water. On occasion, babies release the meconium into the amniotic fluid, but when that doesn’t happen, it can be used to test for the presence of drugs.

Meconium drug testing is most commonly used for detecting fetal drug exposure and it can detect whether the mother has been consuming cannabis. The detection period is the last 4 to 5 months of pregnancy, or the later stages of the second trimester, and the full third trimester. 

If meconium is unavailable for testing, doctors turn to hair testing (if the baby has enough hair samples in order for the test to be performed) or testing the umbilical cord tissue.   

A multicentered study in Utah and New Jersey concluded that the umbilical cord test can provide faster results compared to meconium testing, as babies may take a few days to pass meconium. This test can be done to check for fetal exposure to cannabinoids, and also methamphetamine, opiates, and cocaine.

Cannabis Use and Breastfeeding

The American College of Obstetricians and Gynecologists and the American Academy of Pediatrics both advise breastfeeding mothers against the use of cannabis as it can be the reason that harmful chemicals pass through the breast milk to the infant. 

A study done by the Memorial University School of Pharmacy in Newfoundland showed that THC is present in breast milk only an hour after initial consumption and can last up to 6 days in the breast milk. Cannabis exposure may be the cause for infants experiencing cognitive, social, and motor defects, and some of them may even have long-lasting effects.

What if You Test Positive for Cannabis Use While Pregnant?

There are cases where women aren’t aware of being pregnant and they’ve been consuming cannabis in their first trimester. If you’re one of those women and you’ve just found out that you’re expecting a baby, our advice would be to stop using it immediately. It would be best to talk to your healthcare provider as they will have all the information and give you the best care possible.

Sometimes, mothers suspected of substance abuse may be tested for drugs. In the case where the test results are positive, the hospital needs to inform Child Protective Services (CPS), and you may be subjected to regular drug tests in the following months. 

This doesn’t mean that your child will instantly be taken away from you, although CPS will keep a close eye on you. The use of marijuana is illegal in most states around the world, especially when it comes to pregnant women, so do the smart thing and stay away from cannabis for the duration of your pregnancy and breastfeeding period.

Final Thoughts

Drug use, similar to alcohol use and tobacco use, isn’t recommended during pregnancy and breastfeeding in order for your baby to grow in as benign an environment as possible. 

Even though smoking marijuana has been legalized for both medicinal and recreational use in some countries, the fact is that it’s still a drug and may result in an impact on cognitive functions.

Expecting mothers should aim to provide the proper prenatal care for their babies in order to have a healthy pregnancy and baby, and that includes refraining from marijuana use for the time being.


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