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More and more women are using marijuana before or during pregnancy to relieve nausea, pain, stress, and promote sleep. In fact, research has found that use has more than doubled in the last two decades.
Marijuana use during pregnancy has been associated with adverse outcomes for the baby, such as lower birth weight, preterm birth, and higher rates of admission to neonatal intensive care units.
What about the potential harm to the mother if she uses cannabis before or during pregnancy? According to a new study, the news is also alarming. There is an increased risk of serious, life-threatening maternal complications, such as gestational hypertension and preeclampsia, two high blood pressure disorders.
“Pregnant people who used cannabis early in pregnancy, or who did not use cannabis, had a 17 percent higher risk of gestational hypertension (and) an 8 percent higher risk of preeclampsia,” said study lead author Kelly Young-Wolff, a research scientist in the Kaiser Permanente research division in Pleasanton, California.
People who used marijuana early in pregnancy also had “a 19 percent increased risk of placental abruption,” Young-Wolff said.
In the case of placental abruption, the organ that supplies oxygen and nutrients The placenta, a tissue that suddenly detaches from the fetus, endangers the health of the mother and the developing baby. Detached placenta is one of the leading causes of death in pregnant women and babies.
“Research suggests that pregnant women are bombarded with inaccurate messages from social media, cannabis retailers and their peers that suggest cannabis use during pregnancy is safe,” Young-Wolff said. “Our study provides timely and important data that adds to the growing body of evidence that cannabis use during pregnancy is not safe.”
Compared with the weight gain considered optimal for a successful pregnancy, people who used marijuana before or early in their pregnancy were 9 percent more likely to gain too much weight and 5 percent more likely to not gain enough weight during their pregnancy, the study found.
“To my knowledge, this is the largest study to date on cannabis use during pregnancy and adverse health effects on the mother,” Brianna Moore, an assistant professor at the Colorado School of Public Health in Aurora, Colorado, said in an email. Moore, who studies cannabis use during pregnancy, was not involved in the new research.
“It’s never too late to reduce or limit your cannabis use during pregnancy to minimize potential health effects,” Moore said. “Talk to your healthcare provider.”
Gestational hypertension is diagnosed when the mother-to-be’s blood pressure rises above 140/90 after the first 20 weeks of pregnancy, usually returning to normal after birth. According to the Children’s Hospital of Philadelphia, consistently high blood pressure during pregnancy can “impede blood flow to many of the mother’s organ systems, including the liver, kidneys, brain, uterus, and placenta.”
In some women, gestational hypertension can progress to preeclampsia, a more serious form of high blood pressure in which increased blood levels of liver enzymes and protein in the urine are signs of possible kidney or liver damage in the mother. Blood platelet levels may decrease, and fluid may build up in the lungs, causing shortness of breath, according to the Mayo Clinic.
In extreme cases, such high blood pressure can lead to blood clots, seizures, stroke, temporary kidney failure and liver complications, according to the Cleveland Clinic.
“Preeclampsia can also lead to preterm delivery and admission to the neonatal intensive care unit, which separates mother and baby at the time of birth and can interfere with that initial skin-to-skin bonding ability,” Dr. Deborah Ansley, an obstetrician-gynecologist and medical director of the Kaiser Early Start Prenatal Health Program in Northern California, said via email. She was not involved in the study.
How can marijuana have such serious consequences during pregnancy? Experts believe that cannabinoids, including tetrahydrocannabinol, or THC, can bind to receptors in the placenta, disrupting estrogen signaling and affecting placental development and function.
THC is the part of the cannabis plant that creates euphoria, but over 100 other cannabinoids have been identified in the cannabis plant, along with over 500 other chemicals.
The study, published Monday in the journal JAMA Internal Medicine, draws on health data from Kaiser Permanente Northern California, which provides health care to 4.6 million people. More than 250,000 pregnant women were asked about their marijuana use when they entered prenatal care, at about 8 to 10 weeks gestation. Many of these patients also underwent a urine test that could detect any marijuana use in the previous 30 days.
More than 20,000 people have been identified as cannabis users, including nearly 11,000 pregnant women who did not admit to using marijuana but tested positive in a urine test.
“Our study was unique in that we had a large enough sample size to conduct a sensitivity analysis that restricted the sample to pregnant patients who had not tested positive for other substances,” Young-Wolff said.
“It is important to note that the results of this analysis followed the same general pattern as the main findings, indicating that our results were not attributable to the use of other substances during pregnancy,” she said.
The likelihood of developing gestational hypertension increased with frequency of use, with daily users at greatest risk.
“Our previous work has shown that the frequency of prenatal cannabis use is increasing over time, with a greater proportion of those who use cannabis during pregnancy reporting daily use in later years,” Young-Wolff said.
This is particularly worrisome because the potency of marijuana is much greater today than in the recent past, experts say.
The study found that using the pill at least once a month or more was associated with an increased risk of placental abruption. Additionally, the risk of eclampsia, a more serious form of preeclampsia that can lead to seizures and death, was increased, but the risk was not statistically significant, the study said.
One unusual finding was a reduced risk of gestational diabetes. Studies in nonpregnant adults have had mixed results on marijuana’s impact on insulin resistance and metabolic syndrome, a cluster of health problems that can lead to diabetes and other chronic diseases, Moore said.
“Further studies are needed to understand if and how cannabis use during pregnancy may impact the risk of gestational diabetes,” Moore said.
The authors acknowledge that the study has limitations. In particular, they were unable to determine whether marijuana use continued during pregnancy.
“I suspect the health effects would be stronger if the pregnant person continued to use cannabis after the first trimester, but more studies are needed,” Moore said.
Urine tests could only look for THC and no other cannabinoids, and self-report could not determine whether use was due to smoking or edibles, Young-Wolff said. Additionally, because all of the expectant mothers were based in Northern California, a state that legalized medical marijuana in 1996 and recreational sales in 2018, the results may not be generalizable to other populations in the United States.
The results may also not be applicable to the general population “Participants in this study were older, had higher incomes and almost all had private health insurance,” Moore added.
As known health risks associated with marijuana increase, pregnant women should feel free to discuss any cannabis use with their health care provider without fear of retaliation, experts say.
“If a pregnant woman is considering using cannabis during pregnancy to self-treat pregnancy-related symptoms, we encourage her to discuss this with her physician and use interventions recommended by clinical practice guidelines,” Young-Wolff said. “If a pregnant woman does not wish to stop using cannabis, we recommend she try to use it less frequently.”
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