Temporal Changes in the Quantity of Conceptions Influence Preterm Births Rates at the Population Level

The presence of temporalities in conceptions, births, and birth outcomes such as preterm birth are well-known. However, the link between these phenomena has received surprisingly little attention. Drawing on birth certificate data from the United States (2010–2019), we demonstrate how temporal changes in conceptions are linked with birth outcomes. First, we formalize the relationship between temporal variation in conceptions and birth outcomes and provide evidence from simulations on how changes in conception rates affect birth outcomes. Second, we demonstrate the temporal relationship between changes in conception rates and birth outcomes. Third, we illustrate the impact of temporal variation in conceptions on the variation in birth outcomes across different U.S. population groups. Our results show a link between the number of conceptions and the distribution of preterm births, such that a decline in conceptions will lead to a decrease in preterm births eight months after, whereas an increase will lead to the opposite pattern. This link is stronger among groups with higher incidences of preterm birth, such as Black Americans relative to non-Hispanic White Americans. Seasonality in conceptions accounts for about one-tenth of the seasonality in birth outcomes, and this proportion increases among groups with higher incidence rates of preterm birth. This study offers new insights into the demographic determinants of health at birth at the population level.