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Counseling on cannabis use in pregnancy


Talking with our patients

The increase in the use of cannabis before and after pregnancy parallels the movement toward state legalization and decriminalization. Historically, clinicians often have relied on illegality as their main focus of counseling when giving recommendations for cessation and abstinence in pregnancy.2 This approach not only leads to punitive counseling, which can fracture the doctor-patient relationship, but increasingly it is no longer valid. In our changing legal climate, we need to provide medically based counseling and be very clear with our patients that legalization does not equate to safety.

It is important that we neither minimize nor overstate the risks. The evidence base for adverse birth outcomes of cannabis use in pregnancy is quite robust, but the associations can be subtle and are moderated by other behaviors and environmental factors that continue to challenge researchers.

As with alcohol, there likely are dose-or trimester-dependent differences in perinatal outcomes, and it’s quite possible that different cannabis products and routes of consumption have different effects. At this point, however, we don’t know the full story, nor do we know the extent to which the literature is biased toward positive correlations – the reporting of adverse effects – compared with negative findings. It is our job as medical care providers to be comfortable in that gray area and to still counsel patients on what we do know, providing the best-possible medical advice based on the information available to us.

In talking with patients, I explain that cannabis may cause a spectrum of problems and that there certainly are risks. I also tell them that we’re uncertain about the conditions and magnitude of that risk and that some babies who are exposed to cannabis in utero may have no perceivable consequences. Such honesty is important for maintaining trust, especially as some patients may see friends and relatives who also are cannabis users have normal pregnancy outcomes.

Much of my concern about cannabis in pregnancy centers on its effect on the developing brain and on long-term neurologic development. I share this with patients – I tell them that cannabis crosses the placenta and may well affect their baby’s brain as it is developing. I explain that I do not know whether this effect would be big or small, but that it’s not a chance I’m willing to take for their baby.

It is also important to educate patients that cannabis products are untested and unregulated and that they may be contaminated with heavy metals, pesticides, and other toxins that may be harmful to themselves and their babies. Patients also should know that the potency of cannabis has been dramatically increasing; research shows that the tetrahydrocannabinol – the psychoactive component – concentration has tripled over the past 2 decades.7

Research tells us that women who use illicit drugs and alcohol categorically engage in some form of harm reduction once they learn they are pregnant, and the same is true for cannabis. This is seen in dramatically different rates of first- and third-trimester use in the new analysis of NSDUH data; third-trimester use is approximately halved.

Some women will not be able to discontinue use, however, or they may try to quit and fail in their attempts. As we should with substance use more broadly, we must meet patients where they are, view cannabis use as a chronic medical problem, offer our assistance in helping them reduce harms of their use, and understand that quitting is a process.

Screening for mental health disorders and trauma is, of course, especially important in patients who use cannabis and other substances recreationally. In cases of medical marijuana usage, I recommend, as ACOG and other have done, that we discuss the risks and benefits of continuing cannabis versus shifting to alternative medications if options exist.

In any case, we must guard against cannabis use dominating all conversations throughout our prenatal care. All patients should be welcomed, congratulated on their pregnancy and on coming for prenatal care, and engaged in the overall process of optimizing their health and the health of their baby. Like any other health issue during pregnancy, cannabis use needs to be screened for and treated in an evidence-based manner, but it does not define the trajectory or success of a woman’s pregnancy or her ability to be a successful parent.

Dr. Mark is associate professor of obstetrics, gynecology, and reproductive sciences at the University of Maryland School of Medicine.


1. JAMA. 2019 Jul 9;322(2):145-52.

2. Preventive Medicine 2017 May 18;104:46-9.

3. JAMA. 2019 Jul 9;322(2):167-9.

4. JAMA Netw Open. 2019 Jul 3;2(7):e196471.

5. Obstet Gynecol. 2019 May;133(5):952-61.

6. J. Addict Med. 2019 May 10. doi: 10.1097/ADM.0000000000000543.

7. Biol Psychiatry. 2016 Apr 1;79(7):613-9.


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