Acute Placental Inflammation Is Associated with Reduced Progesterone Receptor Density in the Basal Decidua in Spontaneous Preterm Birth

A functional progesterone withdrawal has been thought to contribute to the pathophysiology of spontaneous preterm birth (PTB). The density of the progesterone receptor (PR) in gestational tissues could play a role in functional progesterone withdrawal. We sought to understand the relationship between placental pathology and the density of PR in the basal decidua in the setting of spontaneous preterm delivery.This is a secondary analysis of a retrospective cohort study of 40 patients with spontaneous PTB < 37 weeks from a prior study at NorthShore University HealthSystem previously described. Placental pathology was categorized according to the Amsterdam criteria into acute inflammation (AI), chronic inflammation (CI), maternal vascular malperfusion (MVM), and fetal vascular malperfusion (FVM). Slides containing basal decidua were stained for PR. Ten distinct images were obtained from the basal plate of each placenta. The positive cell detection program in QuPath image analysis software was used to estimate the percentage of cells positive for PR (%PR + ). The mean %PR+ cells were calculated from the ten representative images and were correlated with patterns of placental injury using <i>t</i>-tests. Models were adjusted for gestational age at delivery.The median gestational age at delivery was 32.5 weeks (interquartile range: 30.5, 34.1). There was a lower density of %PR+ cells among those with AI (12.9%PR+ without AI vs. 9.1%PR + with AI, <i>p</i> = 0.03). There were no differences in the percent of %PR+ cells based on CI, MVM, or FVM. Models adjusted for gestational at delivery demonstrated persistent association with PR density and AI and no difference in the other pathologies.The presence of AI is associated with the lower density of PR expression in the basal decidua by quantitative immunohistochemical analysis. Further research is needed to investigate these findings in the context of spontaneous PTL and the prevention of PTB. · AI is associated with a lower density of PR expression.. · PR is expressed in the basal decidua in the placenta.. · Further research is needed to investigate findings in the context of PTB..