Abstract
Objective Marijuana use is associated with placenta-mediated adverse pregnancy outcomes including
fetal growth restriction, but the mechanism remains uncertain. The objective was to
evaluate the association between maternal marijuana use and the feto-placental weight
ratio (FPR). Secondarily, we aimed to compare placental histology of women who used
marijuana to those who did not.
Study Design This was a secondary analysis of singleton pregnancies enrolled in a multicenter
and case–control stillbirth study. Prior marijuana use was detected by electronic
medical record abstraction or cord homogenate positive for 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic
acid. Prior tobacco use was detected by self-report or presence of maternal serum
cotinine. Stillbirths and live births were considered separately. The primary outcome
was FPR. Association of marijuana use with FPR was estimated with multivariable linear
modeling adjusted for fetal sex, preterm birth, and tobacco use. Comparisons between
groups for placental histology were made using Chi-square and stratified by live birth
and stillbirth, term and preterm deliveries, and fetal sex.
Results Of 1,027 participants, 224 were stillbirths and 803 were live births. Overall, 41
(4%) women used marijuana during the pregnancy. The FPR ratio was lower among exposed
offspring but reached statistical significance only for term stillbirths (mean 6.84
with marijuana use vs. mean 7.8 without use, p < 0.001). In multivariable modeling, marijuana use was not significantly associated
with FPR (p = 0.09). There were no differences in histologic placental features among those with
and without marijuana use overall or in stratified analyses.
Conclusion Exposure to marijuana may not be associated with FPR. Similarly, there were no placental
histologic features associated with marijuana exposure. Further study of the influence
of maternal marijuana use on placental development and function is warranted to better
understand the association between prenatal marijuana use and poor fetal growth.
Key Points
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Maternal marijuana exposure was not associated with the feto-placental weight ratio.
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Marijuana exposure was not associated with differences in placental histology.
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Concerning trend toward lower feto-placental weight ratios among marijuana-exposed
stillbirths.
Keywords
placenta - marijuana - feto-placental ratio - stillbirth
