Abstract
Risk of postpartum opioid use disorder or overdose is low among women with prenatal opioid analgesic use.
INTRODUCTION
Four percent of women use opioids for pain in pregnancy in the United States and Canada.1,2 An increased risk of postpartum opioid overdose among women with opioid use disorder (OUD) has been observed; however, the risk of opioid-related harm among women with prenatal opioid analgesic use and no prior OUD is unknown.3–5 We used administrative health data to estimate the risk of and factors associated with postpartum OUD or opioid overdose in prenatally exposed women.
METHODS
We followed a population-based cohort in the single-payer health care system in Ontario, Canada, accessed through linked health administrative data at ICES, an independent, nonprofit research institute whose legal status under Ontario's health information privacy law allows collection and analysis of data, without consent, for health system evaluation. We included women with an estimated due date after April 7, 2013, which corresponded to data availability, through March 31, 2018, with prescription opioid analgesic fills during pregnancy.1 Opioid prescriptions were identified from the linked Narcotics Monitoring System, which records all community pharmacy–dispensed narcotic prescriptions irrespective of payment type. Women with OUD or an opioid overdose 2 years before delivery were excluded. The Queen's University Health Sciences Research Ethics Board approved this study [#6026353].
A priori risk factors included5,6 prenatal opioid analgesic duration, average daily dose dispensed (morphine equivalents), prescribed prenatal benzodiazepines, age, parity, neighborhood-level income quintile, rural residence, social disadvantage, Elixhauser comorbidity score, pain diagnosis, mental health diagnosis, substance use disorder other than OUD, opioid analgesic use 1 year before conception, neonatal abstinence syndrome, and cesarean delivery.
Study outcomes were OUD or opioid overdose within 365 days of delivery, defined as 1) opioid agonist therapy prescription, 2) outpatient opioid agonist therapy visit, 3) emergency department visits or hospitalizations for OUD or opioid overdose, or 4) opioid-related death. Logistic regression models were used to estimate crude and adjusted odds ratios and 95% CIs. Analyses were performed using SAS 9.4.
RESULTS
Of 27,192 women with prenatal analgesic opioid use and no OUD history, 224 (0.8%) experienced OUD or opioid overdose between delivery and 365 days postpartum. Most events were OUD-related (outpatient visit or opioid agonist therapy prescription; n=209) and opioid overdose (n=19); there were no overdose deaths. Women with these outcomes differed from women without on most characteristics (Table 1). In the adjusted model, risk factors included longer prenatal opioid analgesic use, pain diagnosis, mental illness, non-OUD substance use before conception, younger age, and residing in low-income and rural areas.
Table 1.
Factors Associated With Opioid Use Disorder or Opioid Overdose* Between Delivery and 365 Days Postpartum Among Women With Prenatal Prescription Opioid Analgesic Use†
DISCUSSION
In this large cohort study of women exposed to opioid analgesics during pregnancy, the risk of postpartum OUD or opioid overdose was low (less than 1%). However, the odds of such outcomes were increased among women younger than age 25 years, those in low income or rural areas, and those with mental health and addiction diagnoses and 30 or more days of prenatal opioid analgesic use, albeit with modest increases in absolute risk. Outside of pregnancy, longer initial opioid prescription duration, mental illness, substance use, and younger age have been associated with opioid overdose, long-term opioid use, and OUD.6,7 Although neonatal abstinence syndrome risk was too low to explore in adjusted analyses, neonatal abstinence syndrome was a risk factor of postpartum opioid overdose and mortality in Massachusetts, Ontario, and the United Kingdom, presumably due to maternal OUD.5,8 In our cohort, mothers of newborns with neonatal abstinence syndrome used prenatal opioid analgesics for longer durations. Our data suggest that these identifiable clinical factors may also be markers of risk in women without OUD. Study strengths include the comprehensive population-based data, including opioid prescriptions; however, findings may be limited to health care system users and reflect diagnostic code accuracy. These new findings may be useful for physicians treating pregnant and postpartum women for pain. Shorter opioid prescribing and prenatal screening for mental health diagnoses and substance use are recommended.
Footnotes
This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MOH). This study also received funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (1R03HD099617-01, S. Brogly). Parts of this material are based on data compiled and provided by MOH, the Canadian Institute of Hospital Information, and the Registrar General through Service Ontario. The analyses, conclusions, opinions, and statements expressed herein are solely those of the authors and do not reflect those of the funding or data sources; no endorsement is intended nor should be inferred.
Financial Disclosure Andi Camden disclosed that they received funding from the Canadian Institutes of Health Research (CIHR) for a Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarship ($35K/y for 3y), though the submitted work is separate from their doctoral research and was not conducted with their PhD Committee. The other authors did not report any potential conflicts of interest.
Each author has confirmed compliance with the journal's requirements for authorship.
Peer reviews and author correspondence are available at http://links.lww.com/AOG/C490.
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