Distinct preterm labor phenotypes have unique inflammatory signatures and contraction associated protein profiles†.

Preterm labor (PTL) is the predominant cause of childhood morbidity and mortality. It has several phenotypes, each with a distinct etiology often involving inflammation. Here, in samples of reproductive tissues obtained in early PTL from women with phenotypically defined PTL, we examined the presence and distribution of inflammation and its relationship with prolabor gene expression. In chorioamnionitis (CA-PTL), cytokine protein concentrations were increased across all tissues; in idiopathic (I-PTL), the inflammatory changes were limited to the choriodecidua; inflammation was not a feature of placental abruption (PA-PTL). CA-PTL was associated with activation of p65 in the myometrium and AP-1 in the choriodecidua, and PA-PTL with CREB in the choriodecidua. In the myometrium, PGHS-2 mRNA level was increased in CA- and I-PTL; in the amnion, PGHS-2 mRNA level was higher in PA- and I-PTL, while in CA-PTL, OT, OTR mRNA, and CX-43 expression were increased. In the choriodecidua, PGHS-2 mRNA level was unchanged, but in CA and I-PTL, OT mRNA level were increased and OTR was reduced. These data show that CA-PTL is associated with widespread inflammation and prolabor gene expression. In contrast, in I-PTL, inflammation is limited to the choriodecidua, with discrete increases in PGHS-2 in the amnion and OT in the choriodecidua. Inflammation is not a feature of PA-PTL, which is associated with increased OT and OTR in the amnion.