Adverse outcomes in pregnancy occurred more often if the fetus was exposed to cannabis in the early stages of pregnancy, retrospective data from a new multicenter study suggests.  Of more than 9,000 pregnancies analyzed, 4 key adverse pregnancy outcomes occurred in 27.4% of the cannabis-exposed group compared with 18.1% of the non-exposed group.

The findings, reported last month at the Society for Maternal-Fetal Medicine Annual Pregnancy Meeting, were also published in the American Journal of Obstetrics & Gynecology.

The study was ancillary to a prospective nulliparous cohort study involving women recruited at 8 US centers from 2010 to 2013 and used frozen urine samples collected at 6 to 14 weeks’ gestation to determine exposure to cannabis.

Methods, results, and consumption means

The study’s lead author, Torri D. Metz, MD, MS, a maternal-fetal medicine subspecialist, Associate Professor of Obstetrics and Gynecology, and Vice Chair of Research of Obstetrics and Gynecology at the University of Utah Health in Salt Lake City and colleagues analyzed urine samples collected during the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) study, comprised of a large, diverse multicenter cohort of pregnant patients.  Exposure to cannabis was ascertained via urine immunoassay for 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH), and positive results were confirmed using liquid chromatography tandem mass spectrometry.

Of the 10,038 nuMoM2b participants, the researchers included data from 9,257 pregnant women in their first trimester of pregnancy.  After performing their analyses, the data revealed that 540 (5.8%) subjects tested positive for marijuana, meaning those individuals had most likely used cannabis during the first 6 to 14 weeks of their pregnancy.  “The association was robust to multiple sensitivity analyses with covariates including demographics, tobacco and other drug use, medical comorbidities, and psychosocial stress,” the study authors wrote.

The researchers noted that most of the women in the study had smoked marijuana or other cannabis products, since cannabis edibles were not yet widely available during the time frame that the frozen urine samples had been collected.

The clinical cost of exposure

Among the individual components comprising the study’s primary endpoint, most were significantly worse among the group exposed to cannabis.  These included small for gestational age: 9.5% vs 4.1% (P<0.001); hypertensive disorders of pregnancy: 15.9% vs 13% (P=0.049); stillbirth: 1.5% vs 0.5% (P=0.003); and medically indicated preterm birth: 5.2% vs 3.9% (P=0.141).

Legalization spread and impact

“With recreational marijuana use becoming legal in more states, we need better data because patients are interested in understanding the risk of cannabis use in pregnancy so they can make an informed decision,” Metz stated in a news release accompanying the meeting presentation.

According to the National Organization for the Reform of Marijuana Laws (NORML), 37 states and the District of Columbia all have laws permitting marijuana for medical use, as do 4 US territories:  Puerto Rico, the Virgin Islands, Guam, and the Northern Mariana Islands.  In addition, NORML cites that 19 states, the District of Columbia, Guam, and the Northern Mariana Islands have approved adult possession and consumption of marijuana.  Further, Cannabis Business Times reports that 13 more states’ legislatures have cannabis reform laws at various stages moving towards likely approval this year.

The medical literature reflects that legalization can influence choices and behavior.  One recent study recommends health screenings for expectant patients who use cannabis in states where it’s legal after its findings showed that pregnant women were 4.6 times more likely to use the drug for symptom relief compared to areas in which only CBD is permitted (Vachhani et al. 2022).

Public messaging about risk

CDC data show that 16.2% of pregnant women aged 18 to 44 years reported using marijuana nearly every day.  These findings prompted then US Surgeon General Jerome Adams, MD, to convene a press conference in February 2019 warning pregnant women, along with teenagers and young adults, about the dangers associated the drug.

“Not enough people know that today’s marijuana is much more potent than in days past,” Adams stated.  “The amount of THC…has increased 3- to 5-fold over the last few decades.  That is before you take into account concentrated forms such as edibles, oils and laxatives, which can increase THC delivery even further by an additional 3-fold.  This is not your mother’s marijuana.”

Which patient cohorts?

Metz and colleagues found that the women in their study who were exposed to cannabis tended to be younger—only 8% were over age 30 at delivery—compared with 37% of the women who did not show signs of cannabis exposure.  Those exposed were also more likely to be non-Hispanic Black, single and never married, and to have public insurance coverage.

The vulnerable placenta

The adverse pregnancy outcomes are closely related to the function of the placenta, the research team from University of Utah Health hypothesized.  Metz elucidated that the natural endocannabinoid system regulates placenta development, raising concerns that the addition of cannabis could compromise that highly regulated system.

The placenta plays a critical role during pregnancy, providing the fetus with oxygen and nutrients, removing harmful waste and carbon dioxide, and producing hormones that spur fetal development.  Medicine, drugs, alcohol and nicotine can transfer from a pregnant woman’s bloodstream to their baby through the placenta.

“We wanted to look specifically at cannabis use early in pregnancy because that’s when the placenta is forming, and a lot of information we currently have indicates that cannabis use does affect the placenta,” Metz explained.

The next step, stated the researchers, is to examine ongoing cannabis use during pregnancy to determine whether “the window of exposure” matters.

Find the study data, “Early pregnancy cannabis exposure and adverse pregnancy outcomes,” at no cost here.

Clinicians’ Bonus:  More To Know

Resources for you and your patients

For You

In 2021, the Committee on Obstetric Practice of the American College of Obstetricians and Gynecologists (ACOG) reaffirmed its clinical guidance on “Marijuana Use During Pregnancy and Lactation.”  Be sure to review the organization’s latest data and recommendations on the effects of marijuana on pregnancy and lactation, as well as medical marijuana use here.

In 2018, the American Academy of Pediatrics (AAP) released its first official guidelines, advising women who are pregnant or nursing to avoid marijuana use because it isn’t safe for them or their children.  Click to find AAP’s complete Clinical Report, “Marijuana Use During Pregnancy and Breastfeeding: Implications for Neonatal and Childhood Outcomes.”

For Your Patients

CDC publishes a concise, 2-page, downloadable flyer, “Marijuana Use and Pregnancy,” for you to offer patients which cites Fast Facts and Q&As on its consumption and risks to both mother and baby.

ACOG also offers a comprehensive list of 15 patient-directed FAQs and glossary on marijuana and pregnancy.

In addition, the March of Dimes provides an information-rich page of guidance and support for patients regarding marijuana and pregnancy, with valuable hyperlinks including how patients can get help to quit marijuana use.

The contents of this feature are not provided or reviewed by NPWH.