1. health and fitness
2. addiction

30 CME REVIEW ARTICLE
Volume 68, Number 10
OBSTETRICAL AND GYNECOLOGICAL SURVEY
Copyright * 2013
by Lippincott Williams & Wilkins
CHIEF EDITOR’S NOTE: This article is part of a series of continuing education activities in this Journal through which a
total of 36 AMA PRA Category 1 CreditsTM can be earned in 2013. Instructions for how CME credits can be earned appear
on the last page of the Table of Contents.
Pregnancy, Breast-feeding, and
Marijuana: A Review Article
Meg Hill, MBBS,* and Kathryn Reed, MD†
*Fellow, Maternal Fetal Medicine, and †Professor and Head, Department of Obstetrics and Gynecology, The University of
Arizona, Tucson, AZ
Marijuana is a commonly used drug. At present, it remains an illegal substance in most areas of the
United States. Recent controversy regarding the perceived harms of this drug has resulted in debate in
both legal and medical circles.
This review examines evidence regarding the effects of marijuana exposure during pregnancy and
breast-feeding. We examined studies pertaining to fetal growth, pregnancy outcomes, neonatal
findings, and continued development of fetuses and neonates exposed to marijuana through adolescence. In addition, the legal implications for women using marijuana in pregnancy are discussed
with recommendations for the care of these patients.
The current evidence suggests subtle effects of heavy marijuana use on developmental outcomes of
children. However, these effects are not sufficient to warrant concerns above those associated with
tobacco use.
Marijuana is the most commonly used illicit substance in the United States. It is predominantly
used for its pleasurable physical and psychotropic effects. With the recent changes to legislature in
Colorado and Washington State making the recreational use of marijuana legal, marijuana has gained
national attention. This raises the question: If it is legal for a woman to consume marijuana, what is the
safety of this activity in pregnancy and breast-feeding? Moreover, do the harms of marijuana use on
the fetus or infant justify the mandatory reporting laws in some states?
Target Audience: Obstetricians and gynecologists, family physicians
Learning Objectives: After completing this CME activity, physicians should be better able to assess
the prevalence of marijuana use in the general obstetric population, evaluate the fetal, neonatal and childhood outcomes associated with marijuana use during pregnancy and breastfeeding, and care for pregnant
women who are faced with the possible legal implications of screening for drug use.
Cannabis the Drug
Cannabis sativa is grown in many temperate climates.1 Historically, the plant has been used for
its fiber in the fabric industry.1,2 However, the sap
from the plant, which the plant produces in copious
All authors and staff in a position to control the content of
this CME activity and their spouses/life partners (if any) have disclosed that they have no financial relationships with, or financial
interests in, any commercial organizations pertaining to this educational activity.
Correspondence requests to: Meg Hill, MBBS, Department of
Obstetrics and Gynecology, The University of Arizona, 1501 N
Campbell Ave, 8th Floor Tucson, AZ 85724. E-mail: meghanhill@
obgyn.arizona.edu.
amounts in hot climates, can be made into hashish.3
The foliage produced can be smoked or cooked and
ingested.3 In the United States, the most common form
of ingestion is via smoke inhalation either through
rolled cigarettes referred to as joints or through glass
or plastic containers used to concentrate the drug
for delivery.3
Although farming of the C. sativa plant is either
discouraged or illegal in most of the United States, the
plant is commonly found growing in other regions of
the world. Testing of human subjects in Asia where
the plant is encountered shows that Delta 9 Tetrahydrocannabinol (THC) is found in human urine after
ingestion of milk from buffalo that have been feeding
www.obgynsurvey.com | 710
Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Pregnancy, Breast-feeding, Marijuana
on the plants.4 This exposure of humans to the plant
dates back thousands of years. Many cultures have
commonplace uses for the plant in regions where
marijuana has been a part of the local culture for
generations.5
Incidence of Use
Marijuana is commonly used by pregnant women
in the United States.6 However, it is not a legal drug
in the majority of states in America. It can be smoked
or consumed in the form of liquid or solid preparations.3 Studies regarding marijuana use in pregnancy
and during lactation can be confounded by recall
and reporting bias as well as the differing baseline
characteristics of those who use and abstain from
marijuana use. Rates of use are higher in younger
cohorts, with the rates of usage decreasing as women
age.7Y9 Women do use marijuana during their fertile
years.8 Cannabis users are also more likely to be nonHispanic black and be having their first child and are
less likely to have used folic acid supplementation
during their pregnancy.9 There is evidence to suggest
that patients in urban areas, from lower socioeconomic status groups, and from single-parent households have higher rates of use.7,9Y11 Four percent of
doctors self-reported marijuana use in California recently, indicating that marijuana use is not limited
to these groups and is simply more often utilized
among them.12
Use in Pregnancy
Pregnant women use marijuana at a higher rate
during the first trimester, with many reporting a
cessation of use or decreased use by the third trimester.11 Many women report use of the drug in the
months preceding a pregnancy with cessation on discovery of the pregnancy, often in the first or early
second trimester.11
Physiologic and Psychological Effects
of Marijuana
The pleasurable effects of marijuana are usually
described as a feeling of elation or amusement. This
is followed by a sense of calm, an increase in appetite, and relaxation. Medicinal marijuana is frequently
used in adjunctive treatments for AIDS and cancer
patients. Animal studies reflect various effects on
appetite and food intake when the endocannabinoid
system is manipulated.13Y15 Negative experiences
have been reported, including palpitations, anxiety,
and sedation. Rare complications can occur such
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711
as cannabinoid hyperemesis syndrome, which occurs
only with long-term, heavy use of the drug.16,17 The
syndrome is alleviated by abstinence.16,17
Long-term effects of marijuana can be assessed in
both current and previous users. Current, heavy users
do have a decreased cognitive ability, spatial reasoning, and decision making. This reflects acute intoxication.18 Some studies show a persistence of these
effects in abstinent heavy users for several weeks to
months after use.18,19 These effects dissipate with
time, and no consistent effects can be demonstrated
in most studies after a period of months to years.18,19
Use of marijuana in young people has been associated with anxiety and depression.20,21 It is unclear
whether this is related to the demographic reporting
heavy use or to the substance itself. Some evidence
suggests that heavy marijuana use in the teen years
can be related to schizophrenia in later life.22 Whether
this is due the drug or whether the drug is used as a
form of self-medication in these patients is unclear.
Effects in Women
Hormones of women have been studied while they
inhale marijuana at both the follicular and luteal phase
of the menstrual cycle.23 In a placebo-controlled,
crossover trial, women who smoked marijuana during
the luteal phase of the menstrual cycle had a depression of prolactin levels, whereas those inhaling a
placebo did not.23 Similar effects were not seen
during the follicular phase of the menstrual cycle.23
This effect has not been investigated in lactating
women and cannot be extrapolated to this population.
The Pregnant Patient
General Approach to Pregnant Women Using
Illicit Substances
Before initiating a discussion or performing a
screening drug test on a pregnant woman, the provider
should be aware of the reporting laws in the state in
which they practice. Women should be made aware of
any mandatory reporting laws that exist in the state
in which they reside. Likewise, they should refuse
screening if they wish without undue pressure from
their provider.24 Some states have punitive laws
in place that can result in imprisonment or loss of
custody for women using drugs.24Y26 These laws
have consistently been found to decrease compliance
with prenatal care and increase the perinatal mortality rate.25,27 They cast doctors in an adversarial
position with the patient and create a dynamic of
distrust.25 Doctors should use their best judgment in
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712
Obstetrical and Gynecological Survey
documenting drug use in their patients and should
do so only with the understanding of the patient.24
Creating a disclosure in the chart without the patient’s
knowledge may undermine the doctor-patient relationship when evidence of this surfaces later, especially if the disclosure is based on the physician’s
interpretation or assumptions and not on the facts
related by the patient.24 The states that currently have
laws enabling criminal charges for child abuse to
be brought against a woman for use of drugs while
pregnant are Arkansas, Colorado, Florida, Illinois,
Indiana, Iowa, Louisiana, Minnesota, Nevada, Oklahoma, Rhode Island, South Carolina, South Dakota,
Tennessee, Texas, Virginia, and Wisconsin.28 Involuntary commitment to a drug treatment program can
be instituted for use of drugs while pregnant in
Minnesota, South Dakota, and Wisconsin.28 Interestingly Arizona, Georgia, Kansas, Maryland, Missouri,
Oklahoma, Tennessee, Texas, Utah and Wisconsin
are the only states that have expedited drug treatment
available for pregnant women.28 This punitive approach creates a climate in which women are afraid to
seek care.25,27 Considering the measures in place to
make women subject to charges of child endangerment
without realistic hope of treatment in many states as
well as legal precedent including arrest and prolonged
incarceration in South Carolina, it is not surprising
that many women are not forthcoming regarding drug
use during pregnancy.28
The approach to the pregnant patient who discloses
illicit drug use should be impartial and focus on the
health and well-being of both the woman and fetus.
Type, amount, and frequency of the drug used should
be ascertained through either a thorough face-to-face
history or through a screening tool. Providers should
be aware that the context in which they view drug use
during pregnancy may not be the same as that of the
patient. Although marijuana use has historically been
considered an unacceptable behavior, the beliefs of
the general public and policy makers in some states
do not reflect this view. The provider should be aware
that many women view marijuana as a harmless
substance that is not associated with significant negative effects. If the patient sees no detriment from
the use of the drug, she is unlikely to stop, and the
provider’s opinion regarding cessation of use may
not be a powerful motivator to the patient. Providers
should also recognize that patients may choose to
wean marijuana use during pregnancy and increase
their use again following delivery.29
Women should be asked if they feel that their use
is ‘‘out of their control’’ or if they are experiencing
negative life effects because of marijuana use. These
patients fall into a group that should be offered additional counseling and referral to a substance abuse
program as would be offered with other legal drugs
that can be abused, such as alcohol.
Levels Transferred via the Placenta and
Breast Milk
Marijuana enters the bloodstream within seconds
and the brain within minutes when inhaled.30 A longer
time generally elapses before effects when marijuana
is ingested orally. It is a highly lipophilic substance
and hence can be bound to fat stores throughout the
body,31 with a tissue half-life of 7 days.30 The active
drug is metabolized by the liver.30,31 It is not unusual
for heavy chronic users (defined in most studies as
95 joints smoked per week) to have urine toxicology
screens that are intermittently positive for several
months after their last use. Complete elimination after
a single exposure to the drug may take a month.30
Light users have the substance detected in their urine
for days to weeks after use.
Placental transfer to the fetus does occur,30,32 and
this results in detectable cord blood levels of the
drug.32 Levels detected in the cord blood indicate
that the fetus receives a proportionately smaller dose
than does the mother.32 Neonates have tested positive
for marijuana in urine.33
Analysis of breast milk reveals the presence of
marijuana in recent users,33 where it is bound to
proteins.34 However, seeing that the concentration of
protein in breast milk is less than 1%,34 the transfer of
the drug is likely commensurate to this protein level.
One study calculated exposure to the neonate to be
0.8% that of the mother’s exposure.31
Effects of Use on Fetal Outcomes
There are few studies that assess the isolated effects
of marijuana on the developing fetus. The confounding
introduced by polydrug use makes interpretation difficult.35Y39 The most common concurrently used drugs
are cigarettes, alcohol, and cocaine.35,36,39 Tobacco is
an important confounder as the use of tobacco is
highly associated with the use of marijuana in most
studies, and tobacco by itself is associated with effects
on growth.38,40 Studies have reported varying associations including growth restriction, shortening of gestation, and neonatal withdrawal symptoms.37,38,40Y42
Another study reported on altered mRNA expression
in the fetal brain.43 These findings have not been
reproduced in well-designed, rigorously performed
studies. In addition, marijuana is not associated with
birth defects in humans.44
One cohort of 756 pregnant women was followed
up in Colorado.32 Subjects were approached for
Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Pregnancy, Breast-feeding, Marijuana
information on drug use in pregnancy. When asked,
34% affirmed that they had used marijuana during
pregnancy. When controlling for cigarette use, there
were no detrimental effects noted on fetal growth
or fetal neurodevelopmental outcomes when infants
were examined at 24 to 72 hours after birth. There
were also no differences in length or growth when
adjusting for cigarette use, nor was there an increase
in anomalies. The mothers who used marijuana had
a statistically significant higher weight gain during
pregnancy in this cohort.32
Interestingly, this study did report a statistically
significant increased rate of male births in marijuana
users. This effect has been noted in trends in other
studies and may be related to the effects of marijuana
on sperm.40,39 Many of the women using marijuana
had male partners who also used marijuana.
When the Colorado cohort was followed up at 1
year of age, 62 of the infants were reported to have
been breast-fed. Again, differences were not found
between groups. In addition, there was no difference
in age at weaning, suggesting that marijuana was not
detrimental to the suckling behavior of infants or the
maternal production of milk.32
A second cohort of women in Jamaica were followed up during pregnancy and after their deliveries.45 In the cultural context of the region, marijuana is
seen as a medicinal substance. Most women smoked
or drank tea with marijuana contained in it.45 Following birth, 24 babies of subjects using marijuana
and 20 babies of women abstaining from use were
examined. Neonatal outcomes were equivalent in the
first week after delivery in this cohort. At follow-up
30 days after delivery, no detrimental effects of
marijuana use were documented.45 The women who
were habitual marijuana users rated their experience
of motherhood as more fulfilling than those who were
not. These children were again examined at age 5
years, and no deleterious effects were noted.46 Confounders in this study were the different economic
statuses between groups, with the marijuana users on
average having a larger amount of control over the
household income.45
The MHPCD (Maternal Health Practices and Child
Development Study)47 and OPPS (Ottawa Prenatal
Prospective Study) were large prospective cohort
studies carried out in Pittsburg and Ottawa, respectively. These studies aimed to include as many pregnant women as possible and assess drug use and
effects of different ingested substances on pregnancy
and childhood outcomes. They relied on maternal reports of marijuana use both during and after pregnancy.
The MHPCD study was carried out in a higher-risk,
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713
lower-socioeconomic-status group of women than the
OPPS cohort of women. These studies did not find an
association between marijuana use in pregnancy and
immediate pregnancy outcomes such as miscarriage
rates, rates of anomalies, mode of delivery, Apgar scores,
or meconium-stained fluid.8
Fried,39 an author particularly interested in the effects of marijuana on offspring, was involved in the
OPPS cohort. However, before completing this work,
he originally published a study claiming that marijuana causes a neonatal abstinence syndrome, not
unlike that of narcotic withdrawal, which results in
neonates exhibiting high-pitched cries and startles and
poor visual habituation, which resolved within a few
days of birth.39,41 This study relied on maternal report
of marijuana use, and there was no mention of testing for use of additional drugs such as heroin or
prescription narcotics. In both of the studies from
Jamaica and Colorado, the cohorts were specifically
examined for these same signs and symptoms in neonates of mothers who used marijuana. These findings
could not be reproduced, with no apparent withdrawal effects in neonates. This seems congruent with
the adult response to marijuana, which does not seem
to cause a significant withdrawal phenomenon.
Effects of Use on Childhood Outcomes
The MHPCD and OPPS cohorts of children were
reexamined regularly during their childhood.36,47Y49
A battery of psychological tests was carried out on
these children addressing broad areas such as global
intelligence quotient and specific neurologic functions pertaining to auditory processing, spatial reasoning, and accuracy. The problems encountered in
these cohorts were the small numbers of ‘‘heavy’’
marijuana users and the confounding introduced by
the social determinants of health and use of other
drugs concurrently with marijuana.36,48
Neither study demonstrated a convincing difference in global IQ of offspring at any age when taking
light or moderate use into account.49 Many associations that were statistically significant ceased to be
so when confounding factors were adjusted for.36,48
Subtle effects were suggested in the ability of children
to comprehend language at age 2 years. However,
after adjustments were made for other determinants of
outcomes such as specific aspects of the home environment, this finding did not persist.49 At this age,
the children of moderate users actually performed
better at motor tasks.50 Some testing showed decreased ability of children to analyze visual stimuli.49
This area requires more study as effects noted in
these studies were subtle. These studies also noted
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Obstetrical and Gynecological Survey
differences in functioning in children exposed to prenatal cigarette smoking as it related to visual analytic
function.49 The findings were in a different facet of
function but did nonetheless confound the findings
related to marijuana, as in North America, marijuana
is generally mixed with tobacco and then smoked.
Heavy use of marijuana (95 joints per week) during
pregnancy was associated with an increase in omission
errors in offspring, highlighting the fact that significant
use may be required to produce a cognitive effect.49
Additional findings were that teachers rated children
of marijuana users as more impulsive, and parents
rated the children as being less attentive. Interpretation of this finding is difficult because marijuana
users had a lower average income, were more likely to
be single parents, and were more likely to use both
alcohol and cigarettes.47,49 The context of this use was
also in locations were marijuana is illegal and associated with risk to the parents of these children should
they be found to be using marijuana, which could in
turn affect the home environment.
When growth trajectories were assessed in the
OPPS cohort, the infants prenatally exposed to marijuana did not have an altered growth pattern when
compared with control subjects after adjusting for
confounding variables.51 There was a smaller head
circumference noted in children of mothers who used
marijuana while pregnant at age 12 years. However,
this finding is based on 19 children of ‘‘heavy’’ users
compared with 93 control subjects and 23 ‘‘light’’
users.51 This finding again ceased to be statistically
significant by midadolescence.8
The Jamaican cohort was also followed to age 5 years
with no differences in children of mothers who continued to use marijuana to those who never used the
substance. The Colorado cohort did not show any
deleterious effects of marijuana use through pregnancy and breast-feeding, although this cohort was
not followed up past 12 months of age.
One report focused on the effect of prenatal marijuana exposure on the incidence of childhood leukemia.52 There was an increase in this disease in
exposed offspring. However, they also noted an increase in leukemia in offspring of pregnancies treated
with antinausea medication. The authors supplant that
the use of pesticides on the marijuana inhaled by study
subjects may have been related to the increased risk of
leukemia.52 Certainly, recall bias is also a consideration in this retrospective cohort.
Effects on Adolescent Outcomes
The OPPS and MHPCD cohorts were followed
by researchers from infancy into late childhood, and
Fried et al53Y55 continued to publish the findings of
research with the OPPS cohort into the children’s
teens. The findings from the OPPS cohort suggested
that growth and specifically head circumference were
not statistically significantly different between groups:
nonusers, light, moderate, and heavy users throughout early childhood. However, at follow-up at age
12 years, the difference in head circumference reached
statistical significance for the maternal ‘‘heavy marijuana use’’ group. This could reflect a true causeand-effect relationship, or it could reflect the higher
levels of alcohol and tobacco use in women who
admitted to heavy use of marijuana.11 In addition,
the number of patients followed up was small, only
20 and 19 in the moderate and heavy use groups,
respectively. Another study assessed the adolescent
brain with the utilization of magnetic resonance imaging. Findings suggested that as the mother accrued
illicit substance use in pregnancy, the brain volume of
the offspring was found to be decreased in adolescence. However, this study focused on cocaine use
with or without concomitant use of other drugs, including marijuana.56
On cognitive testing, the OPPS and MHPCD cohorts were found to have differences noted in early
adolescence. Executive function seemed affected
with omission errors more common in the group
of children with heavy exposure to maternal marijuana.54 IQ was not affected, however.53 This is in
stark contrast to the findings in the same study of a
comparison group: the children of cigarette smokers.
The children of heavy tobacco smokers had more
prominent effects, including differences in perception and statistically significant lower global intelligence scores.53
Effects of Marijuana During Breast-feeding
There is inadequate evidence to make a statement
about the isolated use of marijuana in breast-feeding
mothers. The studies that address this issue are confounded by the fact that few women have isolated use
during breast-feeding in the absence of additional
prenatal use of marijuana. The OPPS, MHPCD, and
Jamaican and Colorado cohorts followed up women
and children exposed to marijuana in pregnancy and
breast milk, with the results discussed above.
Several articles have been published outlining the
risks of marijuana and breast-feeding and defining use
as a contraindication to breast-feeding. The concern
is that marijuana causes an immediate threat to the
health and safety of the child either through sedation of the child if breast-fed while the mother is
using marijuana or through negligent behavior by the
Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Pregnancy, Breast-feeding, Marijuana
mother who uses marijuana.57,58 It should be noted
that these articles are based on opinion and not on any
scientific evidence. An extensive literature review
was unable to yield a single case report of a neonatal
death from exposure to marijuana. One study did find
an effect of marijuana on isolated motor, but not
mental, development at age 1 year in infants exposed
during breast-feeding. The 10 infants in this cohort
exposed only prenatally did not have any motor deficits when compared with control subjects. This study
was confounded by socioeconomic factors and included only 14 women who were using marijuana
while breast-feeding but not while pregnant.59
Cigarette smoking can be used as a surrogate for
marijuana smoking in some respects, although there
is an association with maternal cigarette smoking and
sudden infant death syndrome, where one does not
exist for maternal marijuana use.60,61 A concerning
feature of advising women to ‘‘protect’’ their child by
not breast-feeding is the continued environmental exposure to marijuana and tobacco smoke in the home
without the protective effects of breast-feeding. There
is evidence that women who use recreational drugs
are less likely to breast-feed,10 although this has not
been seen in all cohorts, with women in the OPPS with
little effect of marijuana on the method or duration of
breast-feeding.51 It may be that women are reliant on
the advice of physicians, nurses, and lactation consultants to guide their decisions regarding method of
feeding for their infants. These conflicting results may
reflect different comfort levels with breast-feeding in
the setting of marijuana use.
Several publications have recommended that patients not smoke tobacco while they are pregnant or
breast-feeding.60,62Y64 The basis for this is evidence
that cotinine and nicotine (contained in cigarette
smoke) can be detected in breast milk and in the urine
of newborn babies who breast-feed from mothers
who smoke.65,66 Bottle-fed children of mothers who
smoke also have cotinine detected in their urine.65
However, if patients do smoke tobacco, it is recommended that they should continue to provide the
protection of breast-feeding to their children because
of the multiple health benefits to the child.60,64,67 The
benefits of breast-feeding mitigate some of the risks
associated with neonatal exposure to passive cigarette
smoke, such as sudden infant death syndrome, ear
infections, abnormal weight gain, and hospitalization
for bacterial and viral infections.60,64,67 If a mother
chooses to use marijuana, it may be advisable for her to
breast-feed to mitigate some of the effects of passive
smoke exposure. This becomes especially important
advice in the setting of escalating use, as there is
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715
evidence that tapered use tends to increase again after
delivery.7,29
It is prudent to advise women that if they choose to
smoke marijuana; they do so away from their children (preferably outside the house) and change their
clothing after use, so as to not expose their children
to smoke particles in clothing. This advice is in line
with what is recommended to mothers who smoke
tobacco. There is no adequate evidence to address
whether orally ingesting marijuana may be safer for
the neonate, although this would certainly eliminate
the concern regarding inhalation of smoke particles.
Legal Implications
Mandatory reporting of drug use in pregnancy is a
reality that persists in many states. The American
College of Obstetricians and Gynecologists has made
it clear that women should not be tested without their
consent and that punitive measures dissuade patients
from prenatal care and actually increase perinatal
mortality.27 Women have been prosecuted for the
use of marijuana and other illicit substances.8,26,27
The treatment of a woman as a child abuser in this
circumstance reduces her status to that of a carrier,
existing only to house the fetus without the right
to make her own decisions as an entity with separate rights.27
Physicians should be cognizant of the laws in their
state of practice and consider the screening methods
used in their institutions. Common indications for
drug testing in pregnant women are preterm labor,
hypertension in pregnancy, and placental abruption.
Marijuana use has not been associated with any of
these complications in the large cohorts discussed in
this article; hence, the indication for toxicology for
THC is not indicated in this setting. It may be wise to
omit THC testing in the setting of medical complications and restrict testing to cocaine and methamphetamine if symptoms suggest their use, as these
drugs can be associated with pregnancy complications
such as placental abruption and acute hypertensive
episodes. Many physicians order this test without the
patient’s knowledge in the setting of poor compliance
with prenatal care. These patients are often in disadvantaged economic groups and are more frequently
African American patients.25 Indeed, the disproportionate pursuit of legal action against African American
patients for drug use has been noted.26 As previously
discussed, testing patients for drug use without their
knowledge, consent, or medical indication only serves
to strain the physician-patient relationship and dissuade the patient from prenatal care.25,27
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716
Obstetrical and Gynecological Survey
In the newborn period, positive toxicology may
also present challenges in the new family when there
are differing opinions as to whether marijuana is
contraindicated in breast-feeding. Other substances
found in breast milk with moderate use such as cotinine, caffeine, and alcohol are generally not seen as a
contraindication to breast-feeding.68 However, marijuana is more controversial, probably because it remains an illicit substance in most states. For this
reason, the author suggests that physicians consider
whether screening for marijuana use is indicated in
the setting in which they practice. If a positive screen
is present in a mother who wishes to breast-feed, she
should be made aware that there is no consistent
evidence of severe, ill effects with marijuana and
breast-feeding, but that long-term neurodevelopmental
outcomes are not fully investigated, and there may
be an association with harm in women who smoke 5
or more joints per week both while pregnant and
during breast-feeding. The best advice is to abstain
from marijuana completely seeing that it seems to
have similar effects to cigarettes, but that breastfeeding is an option. Least preferable is continuation
of marijuana use in conjunction with bottle-feeding.
This results in passive smoke exposure without the
benefits of breast milk. As mentioned above, the effects of heavy tobacco use are more striking than those
of marijuana use, and tobacco remains a legal drug.
SUMMARY
Marijuana may be inhaled or ingested and is primarily used by pregnant women for recreational
purposes, although it does have medicinal properties.
Marijuana does cross the placenta and can be detected
in newborn infants. It can also be detected in breast
milk after recent maternal use. Although some studies
report specific effects of marijuana on the developing
brain of the fetus and neonate, these effects are
not reproducible. Heavy marijuana smokers do have
babies who are smaller than those of nonusers. This
finding is confounded by the concurrent use of cigarettes and other illicit substances in most studies
reporting this effect and consistent with the evidence
that heavy tobacco use also results in a lower average
birth weight. Patients should be cautioned that inhaled marijuana may have effects on fetal growth
similar to those of cigarette use. Neurodevelopmental outcomes seem similar between babies of nonusers and users with no resultant effects on global
intelligence quotient. There may be some effects
on visuoperceptual ability, reasoning and attention
noted in older children. These findings have been
reproduced in 2 large cohorts, and the association was
statistically significant only with prolonged, heavy
maternal use (95 joints per week throughout pregnancy and breast-feeding). If these effects do exist
with light, moderate, or sporadic use, they are sufficiently subtle as to not be consistently demonstrated
between studies. The effects of marijuana on the developing fetus and child are subtly different from, but
not evidenced to be more severe than, those of heavy
cigarette consumption by the mother during pregnancy and early childhood. Based on these findings,
mandatory reporting of marijuana use during pregnancy and punitive measures related to the use of this
drug during pregnancy or breast-feeding do not seem
medically warranted. A consistent message of ‘‘breast
is best’’ seems appropriate for mothers who continue
to use marijuana while breast-feeding.
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