Introduction: Accurate molecular mechanisms regulating labor, are not fully elucidated. Knowing both normal and abnormal labor is important for developing and use of advanced and more suitable measures for preventing preterm labor. Purpose: We wanted to present and condense most recent evidence based knowledge about molecular mechanisms, that trigger labor. We will describe specific hormones or factors present during labor and main mechanisms responsible for preterm labor. Methods: We used descriptive method with systematic overview of professional and scientific literature regarding molecular mechanisms regulating labor. Existing scientific literature was acquired through data bases CINAHL, MEDLINE, Pubmed, DiKUL and cooperative bibliographic system COBISS.SI. Results: Mechanisms, sustaining pregnancy and triggering labor, are very complex and include mother, fetus and its membranes. Uterus and placenta have an important role for synthesis and release of labor mediators. Final common pathway is composed by inflammatory and endocrine interactive paths, which lead uterine contractility and cervical dilatation. Clinical research showed that activation of fetal hypothalamic-pituitary-adrenal axis contributes to labor onset. Fetuses’ cortisol level increase affects PGHS expression in placenta, which consequently results in increased prostaglandin activity. Other mechanisms like in progesterone level decrease, estrogen level increase, CRH action, increased sensitivity to oxytocin and gap junction formation are key for successful birth. Discussion and conclusion: Animal research and clinical observation of humans are key for explanation of mechanisms. So far, scientists found out that these mechanisms include fetus’ organs, which are functionally integrated with placenta and uterus. Unfortunately, detailed mechanisms that affect target tissues in uterus and cervix are not discovered so far. Current mechanism understanding has important role in detecting preterm labor. Because of connection between the perinatal morbidity and preterm or post-term labor, scientists developed procedures to successfully prolong pregnancy or result in labor induction.
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