A recent population-based retrospective cohort study published in JAMA Internal Medicine has explored the associations between prenatal cannabis use and maternal health outcomes during pregnancy. The study analysed pregnancies in Northern California from January 2011 to December 2019 and evaluated whether in utero exposure to cannabis is linked to various adverse maternal health conditions.

Study Design and Participants

The study included pregnancies that lasted 20 weeks or longer and were screened for prenatal cannabis use. A total of 316,722 pregnancies from 250,221 unique individuals were examined. The demographic breakdown of the sample was as follows:

• Asian/Pacific Islander: 26.5% (84,039)
• Black: 6.3% (20,053)
• Hispanic: 26.3% (83,145)
• White: 37.4% (118,333)
• Mean Age: 30.6 years (Standard Deviation: 5.4 years)

Exposure Definition

Prenatal cannabis use was defined based on self-reported use during early pregnancy or positive toxicology test results from universal screening at the entrance to prenatal care (approximately 8-10 weeks’ gestation). The frequency of use was categorised as daily, weekly, monthly or less, never, or unknown. Specific data points included:

• Self-reported Use: 2.9%
• Positive Toxicology Testing: 5.3%
• Both Self-report and Toxicology: 1.8%

Frequency of cannabis use among the study participants was:

• Daily: 0.6% (1,930)
• Weekly: 0.7% (2,345)
• Monthly or Less: 1.5% (4,892)
• Unknown: 3.4% (10,886)

Main Outcomes and Measures

Electronic health record data were used to define the following maternal health outcomes:

• Gestational Hypertension
• Preeclampsia
• Eclampsia
• Gestational Diabetes
• Gestational Weight Gain Greater and Less than Guidelines
• Placenta Previa
• Placental Abruption
• Placenta Accreta
• Severe Maternal Morbidity

Adjusted risk ratios (aRRs) were calculated using a modified Poisson regression to determine the association between prenatal cannabis use and these health outcomes.

Results:

The study found significant associations between prenatal cannabis use and several adverse maternal health outcomes:

• Gestational Hypertension: aRR of 1.17 (95% CI, 1.13-1.21)
• Preeclampsia: aRR of 1.08 (95% CI, 1.01-1.15)
• Weight Gain Less than Guidelines: aRR of 1.05 (95% CI, 1.01-1.08)
• Weight Gain Greater than Guidelines: aRR of 1.09 (95% CI, 1.08-1.10)
• Placental Abruption: aRR of 1.19 (95% CI, 1.05-1.36)

The study noted that the pattern of results was similar when prenatal cannabis use was defined solely by self-report or toxicology testing. Additionally, the associations between the frequency of prenatal cannabis use and outcomes varied with the specific health outcome being measured.

Conclusions and Relevance: The findings suggest that prenatal cannabis use is associated with several adverse maternal health outcomes during pregnancy. Continued research is necessary to understand whether characteristics such as dose, mode, and timing of prenatal cannabis use moderate these associations. (Source: JAMA)