Spontaneous Prematurity, Innate Immune System, and Oxidative Stress at the Maternal-Fetal Interface: An Overview

Despite the multifactorial etiology of prematurity, intra-amniotic infection is present in 25–40% of preterm pregnancies. Bacteria in amniotic cavity synthesize phospholipases associated with the production of prostaglandins that leads to rupture of fetal membranes and uterine contractions. Bacterial pathogen-associated molecular patterns (PAMPs) activate pattern recognition receptors (PRRs) such as Toll-like (TLRs) and NOD-like receptors (NLRs), triggering pathways that culminate in the production of cytokines that further increase prostaglandin release. Importantly, endogenous molecules called damage-associated molecular patterns (DAMPs) released under stressful conditions can also activate PRRs. Risk factors for both preterm labor (PTL) and preterm premature rupture of membranes (PPROM), including infection-induced inflammation, may cause an increase of ROS release and depletion of antioxidant defenses. In spite of the similarity between the pathophysiology of PTL and PPROM, there are significant differences regarding molecular mediators, degree of tissue damage, and oxidative stress present in these two conditions. PPROM seems to be a consequence of notable tissue damage resulting from chronic oxidative stress, while PTL is associated with minimal tissue degradation resulting from acute exposure and greater antioxidant status. A better understanding of prematurity pathophysiology and the differences between PTL and PPROM can benefit therapeutic approaches to prevent these important inflammatory syndromes