Conference Coverage

Toxicology reveals worse maternal and fetal outcomes with teen marijuana use


Key clinical point: Maternal and fetal outcomes were worse when marijuana use was detected by urine toxicology.

Major finding: A composite adverse outcome occurred in 46% of adolescent marijuana users, compared with 34% of non–marijuana users (P less than .001).

Study details: Retrospective cohort study of participants in an adolescent maternity clinic.

Disclosures: The authors reported no conflicts of interest.

Source: Rodriguez C et al. Am J Obstet Gynecol. 2018 Jan;218:S37.



Marijuana use in adolescent mothers was associated with multiple adverse outcomes, including increased risk for stillbirth and preterm birth. Also, hypertensive disorders of pregnancy were higher in marijuana users, according to a study that incorporated universal urine toxicology testing of adolescents.

The study compared maternal and fetal/neonatal outcomes in 211 marijuana-exposed with 995 unexposed pregnancies. Christina Rodriguez, MD, and her coinvestigators found that the risk of a composite adverse pregnancy outcome was higher in marijuana users, occurring in 97/211 marijuana users (46%), and in 337/995 (33.9%) of the non–marijuana users (P less than .001).

Dr. Rodriguez said that since it used biological samples to confirm marijuana exposure, the study helps fill a gap in the literature. She presented the retrospective cohort study at the meeting sponsored by the Society for Maternal-Fetal Medicine.

Previous work, she said, had established that up to 70% of pregnant women who had positive tests for tetrahydrocannabinol also denied marijuana use. “If marijuana use is determined by self-report, some women are misclassified as nonusers,” making it difficult to ascertain the true association between marijuana use during pregnancy and pregnancy outcomes, said Dr. Rodriguez of the University of Colorado, Denver.

Whether marijuana is associated with adverse pregnancy outcomes is an increasingly pressing question given rapidly shifting legislation, said Dr. Rodriguez. “In a state with legal access to marijuana, use is common in adolescent pregnancies,” she said.

Participants who were enrolled in prenatal care through the University of Colorado’s adolescent maternity program, where Dr. Rodriguez is a fellow, and who delivered at the University of Colorado Hospital, Aurora, were eligible to participate; adolescents were excluded for multiple gestation and for known major fetal anomalies or aneuploidy.

In addition to urine toxicology testing, participants also completed a uniformly administered substance use questionnaire. Marijuana exposure was defined as either having a positive urine toxicology result or self-reported marijuana use on the questionnaire (or both). Of the marijuana-exposed pregnancies, 133 (63%) of the adolescents tested positive on urine toxicology, 18 (9%) were positive by self-report, and 60 (28%) had both positive marijuana urine toxicology and positive self-report. Toxicology was available for 91% of participants.

Participants were negative for marijuana exposure if they had a negative toxicology screen, regardless of their response on the substance-use questionnaire.

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