County-level neonatal opioid withdrawal syndrome rates and real-world access to buprenorphine during pregnancy: An audit ('secret shopper') study in Missouri

Background: Amid rising rates of neonatal opioid withdrawal syndrome (NOWS) worldwide and in many regions of the USA, we conducted an audit study (“secret shopper study”) to evaluate the influence of county-level buprenorphine capacity and rurality on county-level NOWS rates. Methods: In 2019, up to three phone calls were made to buprenorphine prescribers in the state of Missouri (USA). County-level buprenorphine capacity was defined as the number of clinicians (across all specialties) accepting pregnant people divided by the number of births. Multivariable negative binomial regression models estimated associations between buprenorphine capacity, rurality, and county-level NOWS rates, controlling for potential confounders (i.e., poverty, unemployment, and physician shortages) that may correspond to higher rates of NOWS and lower rates of buprenorphine prescribing. Analyses were stratified using tertiles of county-level overdose rates (top, middle, and lowest 1/3 of overdose rates). Results: Of 115 Missouri counties, 81(70 %) had no buprenorphine capacity, 17(15 %) were low-capacity (