Reports from Denmark1 and the Limerick region in Ireland2 noted dramatic reductions in preterm births during the initial months of the coronavirus disease 2019 (COVID-19) pandemic. We sought to assess the impact of the COVID-19 pandemic on preterm birth rates in a large racially diverse population during the peak months of the pandemic. Approximately 1 in 8 births in the United States occurs to California residents, a population that is among the most diverse in the country.