1150: Adverse pregnancy outcomes following the assassination of John F. Kennedy in 1963

Abstract

Women exposed to major stressful events during pregnancy are thought to be at increased risk of adverse birth outcomes, but rigorous evidence for this hypothesis is lacking. Therefore, we used a discordant-sibling design, which provides stronger inferences about causality, to examine whether a major stressor during pregnancy (the assassination of John F. Kennedy) resulted in an increased risk of preterm birth. Data were obtained from the Collaborative Perinatal Project, a historical cohort study that enrolled women at their first prenatal care visit from 1959-1965 at 12 sites in the US. Our analysis was restricted to singleton live births ≥24 weeks born before the assassination (n=26,268) or in utero at the time (n=5,833). Exposure was categorized based on trimester of pregnancy. We used survival analysis to evaluate the association between exposure and preterm birth. Models were stratified based on trimester of exposure and adjusted for maternal age, race, parity, education, fetal sex, and study site. We also evaluated associations within sibling pairs discordant for exposure (n=1,528). Sibling models were adjusted for differences in maternal age and fetal sex. Exposure in the first trimester was associated with preterm birth (hazard ratio (HR): 1.18; 95% CI: 1.06, 1.32; Table 1). Results were consistent when preterm birth was defined as < 34 weeks as a sensitivity analysis. In the discordant-sibling model, the point estimate for first trimester exposure was even higher (HR: 1.22; 95% CI: 0.37, 4.06), though because of the smaller N, the confidence interval was wider. Exposure to an acute stressor in the first trimester was associated with preterm birth. This association was present in siblings discordant for exposure, minimizing the possibility it was simply due to genetic differences between women. Limitations include the use of last menstrual period to calculate gestational age. However, results were consistent using a conservative definition of preterm birth. Future work should investigate the underlying biologic pathways of this association.