Marijuana May Sabotage Pregnancy
By Miranda Hitti, August 01, 2006 WebMD,
Marijuana’s active ingredient may thwart
pregnancy, a new study shows.
Marijuana’s key ingredient -- called
tetrahydrocannabinol (THC) -- may make it hard for
a fertilized egg to implant in the womb, says the
study in The Journal of Clinical Investigation.
VanderbiltUniversity’s Haibin Wang , PhD , and
colleagues studied mice, not people. But they
write that their findings have “high clinical
importance” for women.
The bottom line from Wang’s study: If you’re
trying to get pregnant, abstaining from marijuana
may be important for pregnancy success.
Of course, marijuana isn’t legally available in
the U.S. But it’s “still one of the most widely
used illicit drugs in the world, and often by
pregnant women,” write Wang and colleagues.
Tests on Mice
First, Wang’s team let female mice mate with male
mice. Next, the researchers pumped THC into some
of the female mice for four or five days.
For comparison, the researchers pumped other
marijuana chemicals or a marijuana-free substance
(placebo) into other female mice.
The mice started receiving those chemicals when
their eggs had just been fertilized, but before
those eggs had lodged in the womb.
The THC group was least likely to have their eggs
implant in the womb, the study shows.
The scientists traced the problem down to the
nitty-gritty chemical level.
In the mice, THC docked on chemical receptors
usually occupied by another compound called
anandamide. That left anandamide at a loss.
Picture it this way. THC and anandamide are two
types of cars prowling the mall parking lot. They
both want the same type of parking spot; no other
type will do.
The chemical receptor is the type of parking spot
Without THC, anandamide automatically wins. But
when THC is present, it swoops down and nabs the
prized parking spots, leaving anandamide circling
The result: too much anandamide with nowhere to
High anandamide levels disrupt the fine chemical
balance needed for a fertilized egg to move safely
to the womb, note Wang and colleagues.
As a result, the mice in the THC group were more
likely to not have their fertilized egg implant in
the womb, compared with the other mice, the study
Some fertilized eggs just didn’t reach their
destination. Others attached outside the womb in
the ovaries or fallopian tubes, which lead from
the ovaries to the uterus. That’s called an
In women, an ectopic pregnancy is a
life-threatening condition requiring emergency
However, ectopic pregnancy has several risk
factors that are totally unrelated to marijuana.
Wang’s study doesn’t claim to explain all
pregnancy problems in women who use marijuana.
reviewed by Louise Chang, MD
SOURCES: Wang, H. The Journal of Clinical
Investigation, August 2006; vol 116: pp 2122-2131.
WebMD Medical Reference provided in collaboration
with The Cleveland Clinic: “Ectopic Pregnancy.”
News release, The Journal of Clinical