A Retrospective Cohort Study Examining the Utility of Perinatal Urine Toxicology Testing to Guide Breastfeeding Initiation

Objective: National guidelines advise against breastfeeding for women who use nonprescribed substances in the third trimester. This reduces the number of women who are supported in breastfeeding initiation despite limited evidence on the prognostic value of third trimester substance use. We sought to examine the degree to which prenatal nonprescribed substance use is associated with non-prescribed use postpartum. Methods: Retrospective cohort study of pregnant women with opioid use disorder on methadone or buprenorphine between 2006 and 2015. Nonprescribed use was defined by a positive urine drug testing (UDT). Sensitivity, specificity, positive predictive value, and negative predictive value were calculated comparing 3 prenatal periods with postpartum UDT results. Generalized estimating equations were used to examine the extent to which prenatal nonprescribed use was associated with postpartum use. Results: Included were 545 deliveries by 503 women. Mean age was 28.3 years, 88% were White/non-Hispanic, 93% had public insurance, and 43% received adequate prenatal care. The predictive value of UDT's 90 to 31 days before delivery, 30 to 0 days before delivery, and at delivery showed low sensitivity (44, 26, 27%, respectively) and positive predictive value (36, 36, 56%, respectively), but higher negative predictive value (80, 85, and 78%, respectively), P-values all <0.05. In the final adjusted model, only nonprescribed use at delivery was significantly associated with postpartum nonprescribed use. Conclusions: Nonprescribed use at delivery was most strongly associated with postpartum use compared with earlier time periods currently prioritized in guidelines. In women with opioid use disorder prenatal UDT results alone are insufficient to guide breastfeeding decisions.