Abstract
OBJECTIVE: To describe trends in rates of pregnancy, live birth, and gestational outcomes and to assess variation by maternal demographic characteristics. METHODS: We conducted a retrospective cohort study of pregnancies with outcomes at a large and diverse integrated health care system from 2012 to 2023. We calculated temporal trends in unadjusted and adjusted pregnancy rates and live birth rates per 1,000 individuals 15-44 years of age, overall and stratified by age and race and ethnicity. We used quasi-Poisson regression models adjusted for age and self-reported race and ethnicity to estimate the overall percentage change. We also assessed the rates of plurality (per 1,000 pregnancies) and gestational outcomes, including stillbirth, ectopic pregnancy, molar pregnancy, miscarriage, and induced abortion (per 1,000 singleton pregnancies). RESULTS: In total, 700,159 pregnancies from 2012 to 2023 were included. The adjusted pregnancy rate declined from 78 per 1,000 individuals 15-44 years of age in 2012 to 70 in 2023 (-10.2% [95% CI, -15.6% to -4.5%]), and the adjusted live birth rate declined from 53 per 1,000 individuals 15-44 years of age in 2012 to 45 in 2023 (-13.8% [95% CI, -19.3% to -8.0%]). Among singleton pregnancies, the adjusted rates of miscarriage (2012 rate: 166.3 per 1,000 pregnancies; 2023 rate: 162.2 per 1,000 pregnancies, change -2.4% [95% CI, -4.2% to -0.6%]), molar pregnancy (2012 rate: 1.9 per 1,000 pregnancies; 2023 rate: 1.1 per 1,000 pregnancies, change -38.2% [95% CI, -52.1% to -20.2%]), and ectopic pregnancy (2012 rate: 16.7 per 1,000 pregnancies; 2023 rate: 16.3 per 1,000 pregnancies, change -10.3% [95% CI, -15.4% to -4.8%]) declined. The adjusted rate of stillbirth was relatively stable but rare (3.1 and 3.4 per 1,000 singleton pregnancies in 2012 and 2023, respectively; change 5.3% [95% CI, -7.1% to 19.3%]), whereas the adjusted rate of induced abortions increased over time by 27.3% (95% CI, 23.6% to 31.1%) from 133.2 per 1,000 pregnancies in 2012 to 172.4 per 1,000 pregnancies in 2023. CONCLUSION: In an integrated health care delivery system, the pregnancy and live birth rates declined in the past decade, mirroring national surveillance data. The greater decline in live birth rate compared with pregnancy rate may be explained by the higher rate of induced abortion because the rates of other gestational outcomes declined over time.