Survey length may have an impact on response rates. We examined the impact on response rates of adding one or more 12-question supplements to a mixed-mode survey. To respond quickly to emerging issues, short survey supplements on Zika virus and marijuana use were developed for the Pregnancy Risk Assessment Monitoring System (PRAMS), a state population-based survey. In 2016-17, 12 states used the Zika supplement, 4 states used the marijuana supplement, and 2 states included both at the same time. By mail and phone, the supplement was included at the end of the survey. We compared mail and overall response rates after the supplement was implemented to rates immediately before the supplement and to rates at the same time the previous year. Cumulative supplement effects were also examined. Analyses completed to date show that among Zika supplement states, the overall mean response rate dropped (56.4% to 55.2%) after the supplement was added, but among marijuana supplement states the rates increased (59.5% to 60.1%) with addition of supplement; neither change was statistically significant. These results suggest that use of supplements did not systematically decrease response rates.