Most medical professionals advise people who are pregnant to avoid exposure to cannabis. jamie grill atlas/Stocksy
- Researchers say they looked at 9,000
pregnancies and concluded cannabis is associated with a number of
unhealthy pregnancy outcomes.
- They noted that they used testing rather than
self-reporting, as in other studies, because of the amount of
contradictory information about cannabis’ effect on pregnancies.
- The researchers concluded that exposure to
cannabis was associated with a 1.5-fold increase in risk for people who
are pregnant.
Despite cannabis being used as a remedy for a
variety of health issues the past decade as legalization becomes more
prevalent, its effect on pregnant women has been uncertain.
A
The University of Utah researchers looked at more than
9,000 pregnant women from eight medical centers across the United States.
They concluded that
cannabis is associated with “a composite measure of unhealthy pregnancy
outcomes, especially low birth weight, and that higher exposure is associated
with higher risks.”
The study authors wrote that in the past decade the
percentage of people in the United States using medical marijuana has more than
doubled due to legalization in many states.
They also wrote that their study was larger and
measured cannabis exposure more accurately, which had the effect of better
distinguishing cannabis’ effects from those caused by other correlated health
conditions.
“Cannabis use is not safe,” said Dr. Robert Silver, a
University of Utah professor of obstetrics and gynecology and one of the
study’s authors, in a statement.
“It increases the risk of pregnancy complications. If possible, you shouldn’t
use cannabis during pregnancy.”
The study authors added that they wanted to answer
questions about the safety of cannabis during pregnancy, at least partially
because of contradictory information many people get trying to learn about the
health effects of cannabis.
“There’s so much information out there — discussion
and social media channels and on the internet — about cannabis use and
pregnancy,” said Dr. Torri Metz, the
vice chair of research of obstetrics and gynecology at University of Utah and
the study’s lead author, in the statement. “I think it’s hard for patients to
understand what they should be worried about, if anything.”
The research team said some studies found no
association between cannabis use and pregnancy complications. Metz said part of
the reason why different studies get differing results on cannabis and
pregnancy is there are “so many differences between baseline characteristics of
people who use and don’t use cannabis during pregnancy. There’s different rates
of anxiety and depression.”
Details from the pregnancy and cannabis study
The recent study measured the levels of a metabolic
byproduct of cannabis in urine samples, which researchers said gave more
accurate measurements of exposure than in previous studies that relied on
subjects’ self-reporting their use. The latter underestimated the actual
cannabis use rate by two or three times, they said.
The differences can affect risks during pregnancy,
making it difficult to assess the consequences related specifically to
cannabis.
Researchers said the large study size also helped.
Among the subjects, 610 showed detectable levels of
cannabis exposure, meaning the team could statistically untangle cannabis
impact from other factors such as nicotine exposure, pre-existing health
conditions, and socioeconomic status.
The researchers said exposure to cannabis was
associated with a 1.5-fold increase in risk. They added that 26% of pregnant
people exposed to cannabis had an unhealthy pregnancy outcome compared to 17%
of pregnant people who weren’t exposed. Higher risks over the course of
pregnancies came with higher exposure levels.
Researchers examined an aggregate measure of negative
health outcomes, such as stillbirth, pregnancy-related high blood pressure, low
birth weight, and medically indicated preterm birth.
They said these conditions have been linked to reduced
function of the
The study authors said their research couldn’t
determine why cannabis is linked with negative pregnancy outcomes, but
The study data was collected from 2010 to 2014, when
products were just hitting the market and the THC (the psychoactive ingredient in
cannabis) content in newer products has increased. Silver said the greater risk
they found in higher levels of exposure was especially concerning. The effects
of the newer products remain mostly unknown.
The team urged pregnant women considering using cannabis
to talk with their doctor. Pregnant people often use cannabis for nausea or
anxiety, but other remedies have been proven to be safe.
“There are many, many reasons people use cannabis,”
Silver said. “But there may be alternative therapies that can help mitigate the
symptoms.”
Dr. G. Thomas Ruiz,
the lead OB/GYN at MemorialCare Orange Coast Medical Center in California, told Medical News
Today he’s not sure doctors specifically knew cannabis was associated
with low birthweight babies by compromising placenta function. However, it
didn’t stop them from trying to dissuade pregnant women from using cannabis.
“We were very aware of the limited data available of
the results of cannabis use during pregnancy and in general have advised
cannabis users against using cannabis in pregnancy, like the recommendations we
make with other products, such as alcohol or tobacco,” said Ruiz, who was not
involved in the study. “There are also many medications which are safe to use
outside of pregnancy, but that we advise their discontinuation during pregnancy
because of its effect on the developing fetus.”
Ruiz said how the cannabis is ingested probably isn’t
important.
“What is important is the blood level of THC within
the mother and the amount of THC, which crosses the placenta into the
developing fetus,” Ruiz said.
What doctors
think about cannabis use during pregnancy
Dr. Adi Davidov, the
associate chair and director of obstetrics and gynecology at Staten Island
University Hospital in New York, told Medical News Today most doctors just assume
cannabis is unsafe during pregnancy.
“There have been many observational studies looking at
this question that have shown higher pregnancy complication rates,” said
Davidov, who was not involved in the study. “Unfortunately, in an observational
trial, it is hard to prove that there is a direct link, as there are usually
confounding factors. It is unlikely that we will ever have a truly randomized
controlled trial regarding this issue.”
“There is enough observational data in the medical
literature that shows that exposure to marijuana possibly increases poor
obstetric as well as neonatal outcome,” he added.
Dr. Greg Marchand is
an OB-GYN in Arizona who was not involved in the study. He told Medical News
Today this is the first study he’s aware of that disregards subjects’
self-reporting and goes only by lab testing, a method he says “has a lot of
value.”
“That’s going to take out a lot of moms who
occasionally use and might have evaded testing otherwise,” Marchand said. “It’s
also a rather large study, so it adds a lot to the evidence.”
Marchand said how the cannabis is ingested could make
a difference.,
“It is entirely possible that all of the ill effects
seen in this study and many others exist only because of the inhalation of the
smoke, not the actual marijuana,” he said. “This logically makes sense as
similar ill effects are seen when pregnant woman smoke cigarettes. It is very
difficult to subgroup out people who only exclusively inhale vapors or ingest
edibles, as this is a small minority of marijuana users.”
Marchand said he always tells patients not to smoke
marijuana during pregnancy, but it could be a different story if they’re using
edibles or vaping for anxiety, chronic pain, or other medical conditions.
“Regardless of method of ingestion, if they are only
using it recreationally – i.e. to get high – I recommend discontinuing for the
course of pregnancy,” he said.
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