In a new study published in JAMA Pediatrics, researchers at Children's
Hospital Colorado (Children's Colorado) have found that tetrahydrocannabinol
(THC), the psychoactive component of marijuana, stays in breast milk for up to
six weeks, further supporting the recommendations of the American Academy of
Pediatrics, the American College of Obstetricians and Gynecologists and the
Academy of Breastfeeding Medicine to abstain from marijuana use during
pregnancy and while a mother is breastfeeding. This is the first study
examining THC in breastmilk and plasma among women with known marijuana use in
pregnancy since a 1982 study in the New England Journal of Medicine.
"With the increasing utilization of marijuana in society as a whole, we are
seeing more mothers who use marijuana during pregnancy," said Erica Wymore,
MD, MPH, primary investigator, neonatologist at Children's Colorado and
assistant professor of pediatrics at the University of Colorado School of
Medicine on the Anschutz Medical Campus. "However, given the lack of
scientific data regarding how long THC persists in breast milk, it was
challenging to provide mothers with a definitive answer regarding the safety
of using marijuana while breastfeeding and simply 'pumping and dumping'
until THC was no longer detectable in their milk. With this study, we aimed
to better understand this question by determining the amount and duration of
THC excretion in breast milk among women with known prenatal marijuana use."
The researchers studied women with prenatal marijuana use who delivered
their infants at Children's Colorado and UCHealth's University of Colorado
Hospital between November 1, 2016, and June 30, 2019. Specifically,
researchers recruited women who:
- Had a history of marijuana use during pregnancy/a positive urine test for THC when admitted for delivery
- Were over the age of 18
- Had an intention to breastfeed
- Were willing to abstain from marijuana use for six weeks after delivery
- Were willing to provide milk, blood and urine samples during those six weeks
Of the 394 women who were screened, 25 enrolled. Seven of these women were
ultimately able to abstain from marijuana use for the duration of the study.
Reasons listed for the others' inability to abstain included stress, sleep
and pain relief.
The study found that, while the concentrations of THC varied from woman to
woman (likely depending on their level of use, BMI and metabolism), THC was
excreted in the breast milk of these seven women for up to six weeks. In
fact, all of the women still had detectable levels of THC in their
breastmilk at the end of the study.
"This study provided invaluable insight into the length of time it takes a
woman to metabolize the THC in her body after birth, but it also helped us
understand why mothers use marijuana in the first place," said Maya Bunik,
MD, MPH, senior investigator, medical director of the Child Health Clinic
and the Breastfeeding Management Clinic at Children's Colorado and professor
of pediatrics at the CU School of Medicine. "To limit the unknown THC
effects on fetal brain development and promote safe breastfeeding, it is
critical to emphasize marijuana abstention both early in pregnancy and
postpartum. To help encourage successful abstention, we need to look at --
and improve -- the system of supports we offer new moms."
Longitudinal studies from the 1980s have shown that children born to mothers
who used marijuana during pregnancy experienced long-term issues with
cognitive and executive functioning, including impulsivity, as well as
deficits in learning, sustained attention and visual problem-solving skills.
"This study was not about the impact marijuana has on babies, but we are
concerned," said Wymore. "Especially when we consider that today's marijuana
is five to six times higher in potency than what was available prior to
recent marijuana legalization in many states."
Reference:
Erica M. Wymore, Claire Palmer, George S. Wang, Torri D. Metz, David W. A.
Bourne, Cristina Sempio, Maya Bunik. Persistence of Δ-9-Tetrahydrocannabinol
in Human Breast Milk. JAMA Pediatrics, 2021; DOI:
10.1001/jamapediatrics.2020.6098