Characteristics of Prescription Opioid Analgesics in Pregnancy and Risk of Neonatal Opioid Withdrawal Syndrome in Newborns

Abstract

Importance: Prescription opioids are often used during pregnancy even though they are associated with neonatal opioid withdrawal syndrome (NOWS). Most studies of adverse outcomes of opioid use for pain have assessed only the class-wide outcome despite the pharmacodynamic and pharmacokinetic heterogeneity across opioid medications.

Objective: To compare the risk of NOWS across common types of opioids when prescribed as monotherapy during the last 3 months of pregnancy.

Design, setting, and participants: This cohort study analyzed administrative claims data of Medicaid-insured mothers and newborns in 46 states and Washington DC from January 1, 2000, through December 31, 2014. Participants were mothers with 2 or more dispensed opioid prescriptions within 90 days before delivery and their eligible live-born neonates. Data were analyzed from February 2020 to March 2021.

Exposure: Different types of opioid medications were compared by agonist strength (strong vs weak) and half-life (medium vs short and long vs short) of the opioid active ingredient.

Main outcomes and measures: The primary outcome was NOWS, which was identified using an International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic code in the 30 days after delivery. Relative risks (RRs) were adjusted for an exposure propensity score, including demographic characteristics, comorbidities, other medication use, and opioid treatment characteristics (including morphine milligram equivalents), using fine stratification.

Results: The cohort comprised 48 202 opioid-exposed pregnancies with live newborns. A total of 1069 neonates (2.2%) had NOWS and 559 (1.2%) had severe NOWS. Opioid exposure during pregnancy included 16 202 pregnancies exposed to codeine, 4540 to oxycodone, 1244 to tramadol, 260 to methadone (dispensed for pain), 90 to hydromorphone, and 63 to morphine compared with 25 710 exposed to hydrocodone. Demographic characteristics varied across opioids, with tramadol, oxycodone, methadone, hydromorphone, and morphine being more commonly dispensed at older maternal age (≥35 years). Compared with hydrocodone, codeine had a lower adjusted RR of NOWS (0.57; 95% CI, 0.46-0.70), with a similar adjusted RR for tramadol (RR, 1.06; 95% CI, 0.73-1.56), and 2- to 3-fold higher adjusted RRs for oxycodone (1.87; 95% CI, 1.66-2.11), morphine (2.84; 95% CI, 1.30-6.22), methadone (3.02; 95% CI, 2.45-3.73), and hydromorphone (2.03; 95% CI, 1.09-3.78). Strong agonists were associated with a higher risk of NOWS than weak agonists (RR, 1.97; 95% CI, 1.78-2.17), and long half-life opioids were associated with an increased risk compared with short half-life products (RR, 1.33; 95% CI, 1.12-1.56). Findings were consistent across sensitivity and subgroup analyses.

Conclusions and relevance: Results of this study show higher risk of NOWS and severe NOWS among neonates with in utero exposure to strong agonists and long half-life prescription opioids. Information on the opioid-specific risk of NOWS may help prescribers select opioids for pain management in late stages of pregnancy.

Figure 1.. Selection of the Study Cohort

MME indicates morphine milligram equivalent.

Figure 2.. Association Between Opioid Medication Type and Neonatal Opioid Withdrawal Syndrome Risk

Horizontal lines represent 95% CIs. RR indicates relative risk.

Figure 3.. Sensitivity Analyses by Active Ingredient

Horizontal lines represent 95% CIs. MME indicates morphine milligram equivalent; NAS, neonatal abstinence syndrome; NOWS, neonatal opioid withdrawal syndrome; RR, relative risk.

Figure 4.. Sensitivity Analyses by Agonist Strength and Half-life

Horizontal lines represent 95% CIs. MME indicates morphine milligram equivalent; NA, not applicable; NAS, neonatal abstinence syndrome; NOWS, neonatal opioid withdrawal syndrome; RR, relative risk.