Medically Reviewed by
Jason Crawford

Article Last Updated on December 25, 2022

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.”

The Effects of Marijuana On Fetal Development

According to a 2018 clinical report by the American Academy of Pediatrics (AAP), due to the ethical nature of performing clinical studies on cannabis use in pregnant and lactating women, there are no such studies. However, the data we have available from epidemiological and animal studies suggests that prenatal exposure to cannabis can cause serious long-term consequences on neurodevelopmental and behavioral changes in newborns.

Moreover, given our theoretical understanding of the endocannabinoid system and its significance as the bridge between marijuana and the human body, scientists have a reason to believe that the compounds found in marijuana, THC in particular, can negatively affect fetal development.

THC enters the fetal blood circulation through the placenta, after which it crosses the blood-brain barrier, reaching the fat tissue of the fetus’ brain. Since the brain is made up of 60% fat and THC is a fat-soluble molecule, it means that it will stay there longer. Plus, the CB1 receptors, the main cannabinoid receptors that THC attaches to, are found in abundance in the brain, and these receptors are connected to most key functions.

According to the U.S. Food and Drug Administration (FDA), marijuana use during pregnancy can not only result in impaired fetal brain development and low birth weight, but it can also increase the risk of “premature birth and potentially stillbirth.” Apart from THC, other byproducts (such as carbon monoxide) that get released in marijuana smoke are the same ones found in tobacco smoke, which can also be harmful and “result in hyperactivity and poor cognitive function.”

How Long Does Weed Stay In a Newborn’s System?

Weed can be found in a newborn’s system if the mother had been smoking pot or ingesting marijuana in the form of edibles in the last trimester. In this case, the baby may experience temporary withdrawal symptoms, such as crying, sleeping pattern changes, and more frequent tremors. These symptoms tend to subside within about 30 days.

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.


Do you get drug tested at every prenatal visit?

Drug testing at every prenatal visit is currently not legislated by the government and is entirely up to your Ob/Gyn. Normally, urine testing for drug use is not a standard practice unless there is a suspicion. Instead, mothers-to-be still need to have a drug screen done to check for sugar/glucose and ketone levels, presence of proteins, bacteria, and blood cells in the urine in order to check for other health issues that can lead to possible complications like a urinary tract infection (UTI), gestational diabetes, or preeclampsia. However, you should know that if your doctor intends to test you for drug use, they have to ask for your consent.

What do they test the placenta for after delivery?

It is standard practice to examine the placenta after delivery. This procedure is mainly done to confirm that the whole placenta was removed during birth, and also to obtain information about your pregnancy and general health, as well as the gestational age of the pregnancy.

The process includes inspecting the size, shape, consistency, and completeness of the placenta in order to detect any possible abnormalities or infections. This process is especially important if the delivery was significantly difficult or traumatic, and the information obtained can be crucial for further treatment of the mother and the baby, if needed.

Do they test your placenta for drugs?

Testing the placenta for drugs is essential if the mother has a history of drug abuse and in some states, it’s mandated by law. For example, in cases where the mother has a substance disorder that may cause harm to the newborn, a placenta drug test may have to be done. In all other cases, testing the placenta for drugs is optional and up to the parents if they want to find out if any potentially harmful substances can be passed from the mother to the newborn.

What happens if you test positive for drugs while pregnant?

Substance abuse during pregnancy is considered a crime in about half the states in the U.S., and in 19 states it’s even classified as a form of child abuse and neglect. For example, due to the increased prevalence of opioid abuse and overdoses, California, a state where marijuana is fully legal, criminalizes opioid use during pregnancy. Drug use in general, especially opioids, during gestation, is known to lead to significant birth defects and pregnancy complications that can badly affect both the mother and the child – which is why it’s criminalized and taken so seriously. 

Can CPS take my newborn if I fail a drug test?

Many mothers-to-be who are aware of the implications of failing a drug test during pregnancy resort to concealing their drug problem which can hinder them in getting the help they need (and it puts both them and their baby in danger).

Failing a drug test during pregnancy does not warrant the Child Protective Services (CPS) to take your newborn. The protocols may vary from state to state, but generally, the hospital is obliged to notify the CPS so they can record it in their system. Depending on the situation, they may investigate your prescription drug use, including opioids, or they may launch a child abuse investigation if needed. 

By far, opioids, including prescription ones, are considered as particularly dangerous not only because of their side effects but also because of their high addictive potential. If a mother is found to be addicted to opioids, she will be encouraged to get treatment and support during her pregnancy in a way that is safe (for both mother and child).

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.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.