Response to Jansson et al.

Dear Editor:

We thank Drs. Jansson et al. ¹ for their comments in response to the recently revised Academy of Breastfeeding Medicine (ABM) Clinical Protocol #21 on Guidelines for Breastfeeding and Substance Use or Substance Use Disorder. ² We would like to address the issues this protocol has elicited that are specifically in regard to the recommendations on marijuana use.

We do not dispute the metabolism of delta-9-tetrahydrocannabinol (Δ⁹THC) and noted the reference to the 1982 work of Perez-Reyes and Wall ³ in the protocol. ² Likewise, the matter of increased potency was also discussed. However, the research to support other claims is not well established. The article by Liston ⁴ that is referenced was published 17 years ago, and its references are 21–42 years old. As a review, it cites no evidence for the statement “Physiologic effects including sedation and poor feeding have been described in infants receiving breastmilk from marijuana-using mothers.” ¹

There are only three prospective longitudinal human perinatal cohort studies that can be reviewed for neurodevelopmental outcomes of prenatal cannabis exposure. Two of these studies have longer-term follow-up data available as well, as they started their studies during the late 1970s or early 1980s: the Ottawa Prenatal Prospective Study (OPPS) and the Maternal Health Practices and Childhood Development Project (MHPCD). The Generation R study is more recent. These results of all three of these studies over time are summarized in three respective comprehensive articles.^5–7 The physiological and psychological findings correlated with prenatal cannabis exposure thus far are:

• A pattern of inconsistent findings of birth outcomes, although fetal growth may be reduced from midpregnancy onward, eventually leading to lower birth weight when exposure to the plausibly higher levels of Δ⁹THC in the more recent studies is considered. ⁶

• Findings of OPPS and MHPCD do not demonstrate a consistent pattern of adverse neonatal behavior after prenatal cannabis exposure. ⁶

• There is little evidence for a negative effect of prenatal cannabis exposure on cognitive development in early infancy, as only the MHPCD study found lower mental development scores in cannabis-exposed 9 month olds, which disappeared almost a year later. When infants reached the age of 3–4 years, small subgroup analyses in OPPS and MHPCD indicated a negative association between prenatal cannabis exposure and verbal and memory functioning, although the larger and more recent Generation R study did not find evidence for this effect. ⁶

The overall conclusions drawn from these well-referenced analyses are that some evidence points to an adverse effect of prenatal cannabis exposure on fetal developmental outcomes, but the pattern of findings regarding birth outcomes, early neonatal behavior, and infant cognitive development is inconsistent. The more recent Generation R study, with levels of Δ⁹THC likely higher than other studies, reported more inattention and aggression in infant girls exposed to prenatal cannabis use, although this effect may be transient as it disappeared 1.5 years later. ⁷

In sum, there is currently little evidence that prenatal cannabis exposure affects behavioral or cognitive outcomes in the early period. ⁷ Moreover, and to the point, as stated by Calvigioni et al., ⁷ “at the time of this review (2014), no data were available on early exposure to cannabis (with or without tobacco) in early neonatal life, either by breastfeeding or second-hand smoking.” This is key to our studied recommendations on cannabis.

ABM protocols are based on the evidence presented in the literature at the time of writing, and they are for a global audience, not only the United States. An exhaustive search was done to find evidence to support stronger recommendations regarding cannabis use in breastfeeding mothers. But at this time it does not exist. These authors, the ABM Protocol Committee, the ABM Board of Directors, and the expert international reviewers all agreed with our guidance on this subject and unanimously approved this protocol as is our procedure, with the exception of the one protocol committee member who is an author on the letter ¹ to which we are responding. In addition, we remind the readers that each protocol is prefaced by the following statement:

A central goal of The Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

In keeping with this goal and based on this lack of contrary current clinical evidence, we reiterate the following recommendations concerning cannabinoid use and breastfeeding ² :

a. Counsel mothers who admit to occasional or rare recreational use to avoid further use or reduce their use as much as possible while breastfeeding, and to avoid secondary exposure of the infant to marijuana and its smoke.

b. Strongly advise postpartum mothers found with a positive urine screen for Δ⁹THC (indicating prenatal use) to discontinue use of marijuana while breastfeeding and counsel them as to its possible long-term neurobehavioral effects.

c. The lack of long-term follow-up data on infants exposed to marijuana via human milk, coupled with concerns over negative neurodevelopmental outcomes in children with in utero exposure, should prompt extremely careful consideration of the risks versus benefits of breastfeeding in the setting of moderate or chronic marijuana use. A recommendation of abstaining from any marijuana use is warranted.

d. At this time, although the data are not strong enough to categorically recommend abstaining from breastfeeding with any marijuana use, we urge caution.

Our balanced realistic recommendations are in line with other current recommendations,^8–10 including those on Lactmed, the U.S. National Library of Medicine Drug and Lactation database. ⁹ Even a recent comprehensive set of guidelines issued by the state of Colorado strongly discourages marijuana use yet does not advise mothers to stop breastfeeding. ¹⁰

We agree that research is needed to elucidate the exact risk–benefit ratio of breastfeeding in the setting of active maternal marijuana use. In the meantime, continuing to counsel mothers on the potential risk of marijuana with an effort to decrease and stop use is appropriate, but it should not be at a price of discontinuing breastfeeding with the loss of its health benefits to mother and infant when there is occasional marijuana use.