Kelly C. Young-Wolff, PhD, MPH1, Varada Sarovar, PhD1, Lue-Yen Tucker, BA1, Lyndsay Avalos, PhD1, Amy Conway, MPH2, Mary Anne Armstrong, MA1, Nancy Goler, MD3
1Division of Research, Kaiser Permanente Northern California, Oakland CA
2Early Start Program, Kaiser Permanente Northern California, Oakland CA
3Regional Offices, Kaiser Permanente Northern California, Oakland CA
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Kelly C. Young-Wolff, PhD, MPH
Division of Research
Kaiser Permanente Northern California
2000 Broadway, Oakland, CA 94612, USA
For submission to: JAMA Internal Medicine
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Use of marijuana, an antiemetic, is increasing among pregnant women,1,2 and data from two small surveys indicate that women self-report using marijuana to alleviate nausea and vomiting in pregnancy (NVP).3,4 To date, only one epidemiologic study has examined whether women with NVP are at elevated risk of using marijuana. A study of 4,735 pregnant women in Hawaii from 2009-2011 found that self-reported prenatal marijuana use was more prevalent among those with (3.7%) versus without (2.3%) self-reported severe nausea during pregnancy.5
We used data from a large California healthcare system with gold-standard universal screening for prenatal marijuana use via self-report and urine toxicology from 2009-2016 to test whether prenatal marijuana use is elevated among females with a diagnosis of NVP.
Kaiser Permanente Northern California (KPNC) is a multispecialty healthcare system serving >4 million members representative of the Northern California area. The sample comprised KPNC pregnant females aged >12 who completed a self-reported substance use questionnaire and urine toxicology test in the first trimester (at ~8 weeks gestation) from 2009-2016 during standard prenatal care. The KPNC Institutional Review Board approved and waived consent for this study.
NVP in the first trimester was based on ICD diagnoses in the electronic health record and categorized into: severe (hyperemesis gravidarum), mild (other NVP diagnoses), or no NVP.
We estimated the adjusted odds of prenatal marijuana use among females with NVP using multi-level logistic regression in SAS 9.3, controlling for age, race/ethnicity, median neighborhood household income, year, and self-reported marijuana use in the year before pregnancy. Two-sided P-values <.05 were considered statistically significant.
Of 279,457 screened pregnancies from 2009-2016,2 220,510 (78.9%) received the screening in the first trimester. The sample was 36.7% white, 27.1% Hispanic, 16.8% Asian, 5.7% black, and 13.7% other; 1.2% were aged 12-17, 15.3% 18-24, 62.7% 25-34 and 20.9% >35; 17.9% had >1 pregnancy from 2009-2016. The average median neighborhood household income was $74,651 (SD=$30,650) and 8.3% self-reported marijuana use in the year before pregnancy.
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The prevalence of severe and mild NVP was 2.3% and 15.3%, respectively. The prevalence of prenatal marijuana use by self-report or toxicology was 5.3%, and was greater among females with severe (11.3%) and mild (8.4%) versus no NVP (4.5%). Relative to females without NVP, those with severe (aOR=3.80, 95%CI, 3.19-4.52, P<.0001) and mild (aOR=2.37, 95%CI 2.17-2.59, P<.0001) NVP had increased odds of marijuana use (Table).
In a large sample of diverse California pregnant females from 2009-2016 with universal gold-standard marijuana screening, those with severe NVP had nearly 4 times greater odds of prenatal marijuana use, and those with mild NVP had more than 2 times greater odds of prenatal marijuana use than females without NVP. While results are consistent with the hypothesis that women use marijuana to self-medicate NVP, it is also possible that marijuana use contributes to NVP, or that providers diagnose NVP more frequently among women who report using marijuana to treat it.
This study was limited to KPNC pregnant females screened for marijuana use at ~8 weeks gestation and results may not generalize to females without healthcare or those who enter prenatal care late. Providers may not diagnose very mild NVP, and our sample may reflect a more severe subset of NVP patients. We could not distinguish prenatal marijuana use before versus after females knew they were pregnant, and misclassification is possible given variability in the duration that marijuana is detectable in urine.
The health effects of prenatal marijuana use are unclear and national guidelines recommend that pregnant women discontinue use.6 Patients with NVP should be screened for marijuana use and educated about effective and safe NVP treatments.
Acknowledgments and disclosures
This study was supported by a NIH NIDA K01 Award (DA043604) and a NIH NIMH K01 Award (MH103444). The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication. Lue-Yen Tucker and Varada Sarovar conducted the data analysis for this study. Dr. Young-Wolff had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. All authors declare no conflict of interest.
- Brown QL, Sarvet AL, Shmulewitz D, Martins SS, Wall MM, Hasin DS. Trends in marijuana use among pregnant and nonpregnant reproductive-aged women, 2002-2014. JAMA. 2017;317(2):207-209.
- Young-Wolff KC, Tucker LY, Alexeeff S, et al. Trends in self-reported and biochemically tested marijuana use among pregnant females in California from 2009-2016. JAMA. 2017;318(24):2490-2491.
- Mark K, Gryczynski J, Axenfeld E, Schwartz RP, Terplan M. Pregnant women’s current and intended cannabis use in relation to their views toward legalization and knowledge of potential harm. J Addict Med. 2017;11(3):211-216.
- Westfall RE, Janssen PA, Lucas P, Capler R. Reprint of: survey of medicinal cannabis use among childbearing women: patterns of its use in pregnancy and retroactive self-assessment of its efficacy against ‘morning sickness’. Complement Ther Clin Pract. 2009;15(4):242-246.
- Roberson EK, Patrick WK, Hurwitz EL. Marijuana use and maternal experiences of severe nausea during pregnancy in Hawai’i. Hawaii J Med Public Health. 2014;73(9):283-287.
- Committee on Obstetric Practice. Committee Opinion No. 722: Marijuana use during pregnancy and lactation. Obstet Gynecol. 2017;130(4):e205-e209.
TABLE. Adjusted Odds Ratios (aOR) with 95% Confidence Intervals (CI) for Marijuana Use in the First Trimester of Pregnancy (N = 220,510)
|NVP Category||aOR (95% CI)||P|
|No NVP||N = 181,679 (82.4%)||Reference|
|Mild NVP||N = 33,691 (15.3%)||2.37 (2.17, 2.59)||<.0001|
|Severe NVP||N = 5,140 (2.3%)||3.80 (3.19, 4.52)||<.0001|
“Notes. Marijuana use in the first trimester of pregnancy is based on positive self-report or positive urine toxicology screening. Analyses used PROC GLIMMIX and controlled for standard covariates based on prior literature and availability in electronic health records, including age group, race/ethnicity, median neighborhood household income, year, and self-reported marijuana use in the year before pregnancy from the universal prenatal substance use screening questionnaire. All toxicology tests were confirmed with a confirmatory laboratory test. Among pregnant females with a positive self-report or toxicology test, 0.7% were positive on self-report only, 3.1% were positive on toxicology only, and 1.5% were positive on both self-report and toxicology. The median sample size across years was 27,017 (range 26,451–28,149). First trimester is defined as 90 days from last menstrual period. The ICD-9-CM and ICD-10-CM diagnosis codes for NVP identified in our sample included: (1) Severe: 643.00, 643.03, 643.10, 643.13, O21.0, O21.1 (2) Mild: 536.2, 643.80, 643.90, 643.93, 787.01, 787.02, 787.03, G43.A0, O21.9, R11.0, R11.10, R11.11, R11.2.