Pregnancy provides a critical opportunity to engage individuals with opioid use disorder in care. However, before the COVID-19 pandemic, there were multiple barriers to accessing buprenorphine/naloxone during pregnancy. Care disruptions during the pandemic may have further exacerbated these existing barriers. To quantify these changes, we examined trends in the number of individuals filling buprenorphine/naloxone prescriptions during the COVID-19 pandemic. We estimated an interrupted time series model using linked national pharmacy claims and medical claims data from prepandemic (May 2019 to February 2020) to the pandemic period (April 2020 to December 2020). We estimated changes in the growth rate in the monthly number of individuals filling buprenorphine/naloxone prescriptions in the 6 months preceding a delivery claim, per 100,000 pregnancies, during the COVID-19 pandemic. We identified 2947 pregnant individuals filling buprenorphine/naloxone prescriptions. Before the pandemic, there was positive growth in the monthly number of individuals filling buprenorphine/naloxone prescriptions (4.83%; 95% confidence interval [CI], 3.82-5.84%). During the pandemic, this monthly growth rate declined for both individuals on commercial insurance and individuals on Medicaid (all payers: -5.53% [95% CI, -6.65% to -4.41%]; Medicaid: -7.66% [95% CI, -10.14% to -5.18%]; Commercial: -3.59% [95% CI, -5.32% to -1.87%]). The number of pregnant individuals filling buprenorphine/naloxone prescriptions was increasing, but this growth has been lost during the pandemic.