Seatbelt use trends by pregnancy status and state in the United States, 2011-2024

Seatbelts decrease injuries and fatalities in motor vehicle collisions. Most seatbelt use studies are performed at a national or international scale, yet many lack data granularity to evaluate trends in population subgroups that might have differing belt use behaviors, such as pregnant females. Using data from the Center of Disease Control and Prevention Behavioral Risk Factor Surveillance System (BRFSS), this study aims to evaluate geographic differences in habitual seatbelt use and trends over time across respondent factors, focusing on pregnant females.

Weighted responses of "always wearing seatbelt" in the 2011-2024 BRFSS were aggregated by state, year, age group, sex, and pregnancy status and analyzed using a Bayesian zero-one-inflated beta regression. State seatbelt enforcement was coded as primary or secondary and added into the model.

There were 1,149,325 total responses: 585,543 nonpregnant females (33.3% aged 18-29); 23,356 pregnant female (49.4% aged 18-29); and 540,426 males (39.5% aged 18-29). On average, primary enforcement states exhibit increased habitual seatbelt use adjusted for other factors (aOR = 1.63 (95% CrI 1.36-1.97)). In a secondary enforcement state, pregnant females had higher odds vs. nonpregnant females of habitual seatbelt use (aOR = 1.20 (95% CrI 1.02-1.44) for ages 18-29; aOR = 1.20 (0.99-1.42) for ages 30-44). Pregnancy effects were smaller in primary enforcement states. The probability of habitual seatbelt use among pregnant females increased since 2020 (primary enforcement: 0.86-0.88; secondary: 0.80-0.83), but decreased for nonpregnant females during the same period (primary enforcement: 0.85-0.82; secondary: 0.78-0.75). Regional variations in seatbelt use patterns and trends were identified.

Seat belt primary enforcement laws could increase habitual usage, regardless of age group and pregnancy status. Pregnant females continued to have higher habitual seatbelt use, with stronger effects among younger survey respondents. Additionally, we have identified a cluster of states in the Southeast with declining seatbelt use among both pregnant females and males. Better understanding of local enforcement policies and occupant attitudes toward seat belts can help develop interventions aimed at improving seat belt compliance and in-turn occupant safety.