Expert reviewObstetricsMarijuana use in pregnancy and lactation: a review of the evidence
Section snippets
Search methodology
Ovid Medline (PubMed) and Embase were searched on Dec. 11, 2014, for relevant articles. A focused search was conducted with the search terms marijuana and marihuana or cannabinoids and pregnancy, lactation, and outcomes including adverse perinatal outcomes and neurodevelopment. A search without any language or year limits yielded 615 unique citations. Abstracts were reviewed by the authors, and all pertinent articles were obtained and reviewed individually. In addition, references of pertinent
Legalization of marijuana
Currently both recreational and medical marijuana remain illegal by federal law in the United States. However, the legalization of medical and recreational marijuana at the state level is increasing throughout the United States. At this point, 23 states have legalized the use of medical marijuana, and 4 states have legalized both medical and recreational marijuana (Figure).
Attitudes and beliefs
When women have been followed up longitudinally during pregnancy, a decrease in marijuana use has been noted across trimesters of pregnancy. In a 1 year prospective cohort study, marijuana use in pregnancy declined from 32% in the first trimester to 16% in the third trimester.5
Similarly, a longitudinal prospective study on drug use in pregnancy (n = 86), the Development and Infancy Study, found that the percentage of women who used marijuana throughout the pregnancy declined. However,
Screening and testing for marijuana use
The American College of Obstetricians and Gynecologists and the American Academy of Pediatrics support screening all women for drug use at the time of entry to prenatal care.12 Verbal screening for self-reported use was noted to be acceptable to patients in one study.13 Women who report use should then be encouraged to stop and referred to local substance use disorder programs if needed.
Unfortunately, maternal and fetal testing for marijuana exposure is fraught with error.14 Maternal urine
Nausea and vomiting in pregnancy
As with any drug or medication in pregnancy, possible benefits must be weighed against possible adverse effects. There are few data on the possible benefits of marijuana use in pregnancy. Interest in the use of marijuana as an antiemetic has been propagated by its efficacy in oncology patients.17, 18
There are 2 studies investigating the relationship between marijuana use and nausea and vomiting of pregnancy.19, 20 Roberson et al20 used the pregnancy risk assessment monitoring system data (n =
Anesthetic considerations
Marijuana use can affect the safety and administration of anesthesia surrounding delivery. In high doses, marijuana can cause bradycardia and hypotension, but more commonly, low or moderate doses can cause tachycardia.21 If tachycardia is present or marijuana use is suspected, drugs that increase heart rate such as ketamine, pancuronium, and epinephrine should be avoided. Because marijuana is often inhaled, it can also cause upper-airway irritation and edema, making anesthetic administration
Fetal growth
Many of the human studies of marijuana in pregnancy focus on fetal growth (Table 2).4, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 Abnormalities in growth are biologically plausible, given the passage of cannabinoids across the placenta. There are some data suggesting that cannabis affects glucose and insulin regulation and therefore may affect the fetal growth trajectory.25 However, data regarding fetal growth with marijuana exposure are mixed, with some studies demonstrating a
Neurodevelopment
There have been multiple animal studies and retrospective human studies looking at the effect of maternal marijuana use during pregnancy on neurodevelopment, behavior, and intelligence.
Animal studies have shown alterations in neurotransmitter and neuroendocrine systems in the offspring of rodents exposed to cannabinoids. This effect is particularly pronounced within dopaminergic pathways.44 In addition, there have been some animal studies that show a marked increase in hyperactivity and
Breast-feeding
Cannabinoids consumed by lactating mothers reach the newborn during breast-feeding.58 The amount that reaches the infant is estimated at 0.8% of the mother’s exposure.59 There is some evidence that marijuana use inhibits milk production by inhibiting prolactin secretion.60
Astley and Little61 attempted to determine the effects of marijuana use on infant development at 1 year. Infants exposed to marijuana during lactation scored poorly on the Psychomotor Developmental Index compared with those
Future research
Despite a large volume of literature on the topic of marijuana in pregnancy, there is still a need for high-quality, contemporary, prospective data to better understand the effects of marijuana use in pregnancy and lactation.
We have identified the following research gaps as areas of focus for future studies: (1) determining whether there is an association between marijuana use and congenital anomalies, spontaneous preterm birth, pregnancy loss and stillbirth, or poor fetal growth by serial
Summary
Summary recommendations for the practicing clinician are listed in Table 5. These recommendations are made after a thorough review of the existing literature but are based on studies of varying methodological quality with mixed results and reflect the opinions of the authors after completing this extensive review. Until further data are available, we should continue to discourage women from using recreational drugs, including marijuana, during pregnancy and lactation, given the uncertain short-
Acknowledgment
We appreciate the work of Lilian Hoffecker, a research librarian at the University of Colorado Health Sciences Library, in assisting with the extensive literature search needed to complete this review.
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2023, Obstetrics and Gynecology Clinics of North AmericaEnteral Nutrition: The Intricacies of Human Milk from the Immune System to the Microbiome
2022, Clinics in PerinatologyDirective clinique n<sup>o</sup> 425b: Le cannabis aux différentes périodes de la vie des femmes — Partie 2: Grossesse, période postnatale et allaitement
2022, Journal of Obstetrics and Gynaecology CanadaGuideline No. 425b: Cannabis Use Throughout Women's Lifespans – Part 2: Pregnancy, the Postnatal Period, and Breastfeeding
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The authors report no conflict of interest.