Cannabis Use in Pregnancy and Neonatal Outcomes: A Systematic Review and Meta-Analysis

Estimating the effects of prenatal cannabis exposure on birth outcomes

BACKGROUND AND OBJECTIVES

Prenatal cannabis use prevalence in the United States has increased. Relaxation of state-level cannabis policy may be contributing to the diminished risk perception of using cannabis. The main psychoactive constituent of cannabis, delta-9-tetrahydrocannabinol, crosses the placenta, interacting with functional cannabinoid receptors in the fetus. Here, we assess the association between prenatal cannabis exposure (PCE) and a set of birth outcomes.

METHODS

Using the Michigan Archive for Research on Child Health, a prospective pregnancy cohort, we linked prenatal survey data with neonatal data from state-archived birth records. Recruitment occurred in 23 clinics across Michigan. Pregnant participants with live birth records between October 2017 and January 2022, after exclusion for missing data on cannabis use, birth outcomes, and covariates, were included in the final analytic sample (n = 584). Analyses involved generalized linear models.

RESULTS

An estimated 15% (95% confidence interval [CI]: 12%, 18%) of participants reported using cannabis during pregnancy. Covariate-adjusted models revealed an association between PCE and birth size (ß = -0.3; 95% CI: -0.5, -0.003).

DISCUSSION AND CONCLUSIONS

Findings suggest a relationship between PCE and smaller birth size. Clinicians should follow guidelines outlined by the American College of Obstetricians and Gynecologists when counseling pregnant patients on cannabis use.

SCIENTIFIC SIGNIFICANCE

We detected a significant association between PCE and birth size. Most studies focus only on the extremes of birth size, however, use of z-scores allow for assessment of the sex-specific birth weight-for-gestational age distribution, increasing the accuracy of detecting an effect of cannabis exposure on birth size.

Influence of substance use on male reproductive health and offspring outcomes

The prevalence of substance use globally is rising and is highest among men of reproductive age. In Africa, and South and Central America, cannabis use disorder is most prevalent and in Eastern and South-Eastern Europe, Central America, Canada and the USA, opioid use disorder predominates. Substance use might be contributing to the ongoing global decline in male fertility, and emerging evidence has linked paternal substance use with short-term and long-term adverse effects on offspring development and outcomes. This trend is concerning given that substance use is increasing, including during the COVID-19 pandemic. Preclinical studies have shown that male preconception substance use can influence offspring brain development and neurobehaviour through epigenetic mechanisms. Additionally, human studies investigating paternal health behaviours during the prenatal period suggest that paternal tobacco, opioid, cannabis and alcohol use is associated with reduced offspring mental health, in particular hyperactivity and attention-deficit hyperactivity disorder. The potential effects of paternal substance use are areas in which to focus public health efforts and health-care provider counselling of couples or individuals interested in conceiving.

Prenatal Cannabis Use and Maternal Pregnancy Outcomes

Importance

Many studies have evaluated whether in utero cannabis exposure is associated with fetal and neonatal outcomes, yet little is known about whether prenatal cannabis use is associated with maternal health outcomes during pregnancy.

Objective

To evaluate whether prenatal cannabis use is associated with maternal health outcomes during pregnancy.

Design, Setting, and Participants

This population-based retrospective cohort study included pregnancies in Northern California from January 2011 to December 2019 that lasted 20 weeks or longer and were screened for prenatal cannabis use.

Exposures

Prenatal cannabis use was defined as any self-reported use during early pregnancy or a positive toxicology test result based on universal screening at entrance to prenatal care (approximately 8-10 weeks' gestation). Self-reported frequency of use (daily, weekly, monthly or less, never, unknown), use defined only by self-report, and use defined only by toxicology test results were examined.

Main Outcomes and Measures

Electronic health record data were used to define the following outcomes: gestational hypertension, preeclampsia, eclampsia, gestational diabetes, gestational weight gain greater and less than guidelines, placenta previa, placental abruption, placenta accreta, and severe maternal morbidity. Adjusted risk ratios (aRRs) were calculated using a modified Poisson regression.

Results

The sample (n = 316 722 pregnancies; 250 221 unique individuals) included 84 039 (26.5%) Asian/Pacific Islander, 20 053 (6.3%) Black, 83 145 (26.3%) Hispanic, and 118 333 (37.4%) White individuals; the mean (SD) age was 30.6 (5.4) years. Overall, 20 053 (6.3%) screened positive for prenatal cannabis use; 2.9% were positive by self-report, 5.3% by toxicology testing, and 1.8% by both. The frequency of cannabis use was 1930 (0.6%) daily, 2345 (0.7%) weekly, 4892 (1.5%) monthly or less, and 10 886 (3.4%) unknown. Prenatal cannabis use was associated with greater risk of gestational hypertension (aRR, 1.17; 95% CI, 1.13-1.21), preeclampsia (aRR, 1.08; 95% CI, 1.01-1.15), weight gain less than (aRR, 1.05; 95% CI, 1.01-1.08) and greater than (aRR, 1.09; 95% CI, 1.08-1.10) guidelines, and placental abruption (aRR, 1.19; 95% CI, 1.05-1.36). The pattern of results was similar when defining prenatal cannabis use only by self-report or only by toxicology testing, and associations between the frequency of prenatal cannabis use and outcomes varied with outcome.

Conclusions and Relevance

The results of this cohort study suggest that prenatal cannabis use was associated with several adverse maternal health outcomes during pregnancy. Continued research is needed to understand whether characteristics of prenatal cannabis use (eg, dose, mode, and timing) moderate these associations.

The longitudinal assessment of prenatal cannabis use on neonatal outcomes

OBJECTIVE

To investigate the association between prenatal cannabis use and perinatal outcomes using longitudinal data from pregnant individuals.

STUDY DESIGN

This secondary-data analysis study utilized data collected from 894 pregnant individuals followed in the Stress in Pregnancy longitudinal study, conducted between 2009 and 2013. The status of cannabis use was ascertained through interviews and electronic medical record reviews to evaluate the effect of cannabis use on perinatal outcomes (NICU admission, preterm delivery, low birth weight, fetal death).

RESULTS

Among participants analyzed, 13.1% used cannabis, who were generally younger (25.9 vs 27.9 years). There was a sevenfold increased risk of fetal death (OR 7.30) among cannabis users relative to non-users. Elevated risk persisted after adjustments of potential confounders (aOR 6.31). Adjusted models also suggested increased low birth weight risk (aOR 1.67).

CONCLUSION

This study highlights an association between prenatal cannabis use and elevated risks for fetal death and low birth weight.

Neonatal outcomes associated with in utero cannabis exposure: a population-based retrospective cohort study

BACKGROUND

The full spectrum of associations between in utero cannabis exposure and adverse neonatal outcomes is still unclear.

OBJECTIVE

This study aimed to evaluate the associations between in utero cannabis exposure and neonatal outcomes.

STUDY DESIGN

This population-based retrospective cohort study of singleton births among Kaiser Permanente Northern California members (January 1, 2011-July 31, 2020) included parent-infant dyads in which the pregnant parent was screened for cannabis use as part of standard prenatal care, generally upon entrance into care. Data were ascertained from electronic health records. Generalized estimating equation models were adjusted for sociodemographic characteristics, other non-cannabis prenatal substance use, medical and mental health comorbidities, and adequacy of prenatal care. In utero cannabis exposure was defined as self-reported use since becoming pregnant and/or a positive urine toxicology test for cannabis at any time during pregnancy (yes/no; primary exposure). Frequency of use was self-reported and categorized as daily, weekly, monthly or less, never, or unknown (secondary exposure). Neonatal outcomes included low birthweight, small for gestational age, preterm birth, neonatal intensive care unit admission, and infant respiratory support.

RESULTS

Of 364,924 infants, 22,624 (6.2%) were exposed to cannabis in utero. After adjustment for potential confounders, including in utero exposure to other substances, in utero exposure to cannabis was associated with greater odds of low birthweight (adjusted odds ratio, 1.20; 95% confidence interval, 1.12-1.28), small for gestational age (adjusted odds ratio, 1.24; 95% confidence interval, 1.18-1.30), preterm birth (<37 weeks; adjusted odds ratio, 1.06; 95% confidence interval, 1.00-1.13), and neonatal intensive care unit admission (adjusted odds ratio, 1.06; 95% confidence interval, 1.01-1.11). There was a suggestive association with early preterm birth (<34 weeks; adjusted odds ratio, 1.11; 95% confidence interval, 1.00-1.23; P=.055), but no significant association with respiratory support (adjusted odds ratio, 1.07; 95% confidence interval, 0.97-1.18). Dose-response analysis found an increasing likelihood of low birthweight and small for gestational age with increasing frequency of prenatal cannabis use by the pregnant individual. Sensitivity analyses further supported an increased likelihood of low birthweight and small for gestational age, although associations with other outcomes did not reach statistical significance.

CONCLUSION

In utero cannabis exposure was associated with increased likelihood of low birthweight, small for gestational age, preterm birth, and neonatal intensive care unit admission. Clinicians should counsel individuals who are pregnant or considering pregnancy about the potential adverse neonatal health outcomes associated with prenatal cannabis use.

Human Milk Cannabinoid Concentrations and Associations with Maternal Factors: The Lactation and Cannabis (LAC) Study

Background and Objectives: As cannabis use increases among reproductive-aged women, there is a growing need to better understand the presence of cannabinoids in milk produced by women using cannabis. It is unclear how concentrations of cannabinoids such as delta-9-tetrahydrocannabinol (Δ9-THC) persist in milk after cannabis use and what factors contribute to variation in milk Δ9-THC concentrations. Our objectives were to measure cannabinoids in human milk following cannabis abstention, after single and repeated instances of cannabis use, and identify factors contributing to concentration variation. Methods: The Lactation and Cannabis (LAC) Study prospectively observed 20 breastfeeding participants who frequently used cannabis (≥1/week), had enrolled <6 months postpartum, were feeding their infant their milk ≥5 times/day, and were not using any illicit drugs. Participants collected a baseline milk sample after ≥12 hours of abstaining from cannabis and five milk samples at set intervals over 8-12 hours after initial cannabis use. Participants completed surveys and recorded self-directed cannabis use during the study period. Results: Δ9-THC peaked 120 minutes after a single instance of cannabis use (median, n = 9). More instances of cannabis use during the study period were associated with greater Δ9-THC area-under-the-curve concentrations (ρ = 0.65, p = 0.002), indicating Δ9-THC bioaccumulation in most participants. Baseline Δ9-THC logged concentration was positively associated with self-reported frequency of cannabis use (b = 0.57, p = 0.01). Conclusions: Cannabinoids are measurable in human milk following cannabis use, and concentrations remain elevated with repeated cannabis use over a day. Substantial variation in Δ9-THC milk concentrations reflects individual differences in characteristics and behavior, including average postpartum frequency of cannabis use.

Cannabis Science and Therapeutics: An Overview for Clinicians

Cannabis-based therapeutics have garnered increasing attention in recent years as patients seek alternative treatments for various medical conditions. This narrative review provides a comprehensive overview of the science behind the medical use of cannabis, focusing on the medical evidence for commonly treated conditions. In addition, the review addresses the practical considerations of using cannabis as a therapeutic agent, offering insights into dosing strategies, variations in cannabinoid formulation, and individual patient responses. Precautions, adverse consequences, and drug interactions are also discussed, with a focus on patient safety and the potential risks associated with cannabis use.

Risk of Adverse Neonatal Outcomes After Combined Prenatal Cannabis and Nicotine Exposure

Importance

The prevalence of cannabis use in pregnancy is rising and is associated with adverse perinatal outcomes. In parallel, combined prenatal use of cannabis and nicotine is also increasing, but little is known about the combined impact of both substances on pregnancy and offspring outcomes compared with each substance alone.

Objective

To assess the perinatal outcomes associated with combined cannabis and nicotine exposure compared with each substance alone during pregnancy.

Design, Setting, and Participants

This retrospective population-based cohort study included linked hospital discharge data (obtained from the California Department of Health Care Access and Information) and vital statistics (obtained from the California Department of Public Health) from January 1, 2012, through December 31, 2019. Pregnant individuals with singleton gestations and gestational ages of 23 to 42 weeks were included. Data were analyzed from October 14, 2023, to March 4, 2024.

Exposures

Cannabis-related diagnosis and prenatal nicotine product use were captured using codes from International Classification of Diseases, Ninth Revision, Clinical Modification, and International Statistical Classification of Diseases, Tenth Revision, Clinical Modification.

Main Outcome and Measures

The main outcomes were infant and neonatal death, infants small for gestational age, and preterm delivery. Results were analyzed by multivariable Poisson regression models.

Results

A total of 3 129 259 pregnant individuals were included (mean [SD] maternal age 29.3 [6.0] years), of whom 23 007 (0.7%) had a cannabis-related diagnosis, 56 811 (1.8%) had a nicotine-use diagnosis, and 10 312 (0.3%) had both in pregnancy. Compared with nonusers, those with cannabis or nicotine use diagnoses alone had increased rates of infant (0.7% for both) and neonatal (0.3% for both) death, small for gestational age (14.3% and 13.7%, respectively), and preterm delivery (<37 weeks) (12.2% and 12.0%, respectively). Moreover, risks in those with both cannabis and nicotine use were higher for infant death (1.2%; adjusted risk ratio [ARR], 2.18 [95% CI, 1.82-2.62]), neonatal death (0.6%; ARR, 1.76 [95% CI, 1.36-2.28]), small for gestational age (18.0%; ARR, 1.94 [95% CI, 1.86-2.02]), and preterm delivery (17.5%; ARR, 1.83 [95% CI, 1.75-1.91]).

Conclusions and Relevance

These findings suggest that co-occurring maternal use of cannabis and nicotine products in pregnancy is associated with an increased risk of infant and neonatal death and maternal and neonatal morbidity compared with use of either substance alone. Given the increasing prevalence of combined cannabis and nicotine use in pregnancy, these findings can help guide health care practitioners with preconception and prenatal counseling, especially regarding the benefits of cessation.

Prenatal delta-9-tetrahydrocannabinol exposure alters fetal neurodevelopment in rhesus macaques

Prenatal cannabis use is associated with adverse offspring neurodevelopmental outcomes, however the underlying mechanisms are relatively unknown. We sought to determine the impact of chronic delta-9-tetrahydrocannabinol (THC) exposure on fetal neurodevelopment in a rhesus macaque model using advanced imaging combined with molecular and tissue studies. Animals were divided into two groups, control (n = 5) and THC-exposed (n = 5), which received a daily THC edible pre-conception and throughout pregnancy. Fetal T2-weighted MRI was performed at gestational days 85 (G85), G110, G135 and G155 to assess volumetric brain development. At G155, animals underwent cesarean delivery with collection of fetal cerebrospinal fluid (CSF) for microRNA (miRNA) studies and fetal tissue for histologic analysis. THC exposure was associated with significant age by sex interactions in brain growth, and differences in fetal brain histology suggestive of brain dysregulation. Two extracellular vesicle associated-miRNAs were identified in THC-exposed fetal CSF; pathway analysis suggests that these miRNAs are associated with dysregulated axonal guidance and netrin signaling. This data is indicative of subtle molecular changes consistent with the observed histological data, suggesting a potential role for fetal miRNA regulation by THC. Further studies are needed to determine whether these adverse findings correlate with long-term offspring neurodevelopmental health.

Prenatal delta-9-tetrahydrocannabinol exposure is associated with changes in rhesus macaque DNA methylation enriched for autism genes

BACKGROUND

With the growing availability of cannabis and the popularization of additional routes of cannabis use beyond smoking, including edibles, the prevalence of cannabis use in pregnancy is rapidly increasing. However, the potential effects of prenatal cannabis use on fetal developmental programming remain unknown.

RESULTS

We designed this study to determine whether the use of edible cannabis during pregnancy is deleterious to the fetal and placental epigenome. Pregnant rhesus macaques consumed a daily edible containing either delta-9-tetrahydrocannabinol (THC) (2.5 mg/7 kg/day) or placebo. DNA methylation was measured in 5 tissues collected at cesarean delivery (placenta, lung, cerebellum, prefrontal cortex, and right ventricle of the heart) using the Illumina MethylationEPIC platform and filtering for probes previously validated in rhesus macaque. In utero exposure to THC was associated with differential methylation at 581 CpGs, with 573 (98%) identified in placenta. Loci differentially methylated with THC were enriched for candidate autism spectrum disorder (ASD) genes from the Simons Foundation Autism Research Initiative (SFARI) database in all tissues. The placenta demonstrated greatest SFARI gene enrichment, including genes differentially methylated in placentas from a prospective ASD study.

CONCLUSIONS

Overall, our findings reveal that prenatal THC exposure alters placental and fetal DNA methylation at genes involved in neurobehavioral development that may influence longer-term offspring outcomes. The data from this study add to the limited existing literature to help guide patient counseling and public health polices focused on prenatal cannabis use in the future.