**1. Introduction**

Cervix uteri is a metabolic active organ, a "gate keeper" in normal pregnancy, an early information prime source about spontaneous preterm birth (sPTB) risks [1], besides other two pathological conditions – preterm/premature membrane rupture (PROM), preterm contractions with which cervical insufficiency/incompetence interlinks in the "Preterm Labor Syndrome" [2], which replaced an earlier five ways acting in cascade/separately: uterine cervical support structures compromise acting alone/associated to the myometrial and membranes over-distension, to decidual hemorrhage, to intrauterine infection/inflammation or to precocious endocrine fetal activation (from maternal or fetal stress) [3]. Vink and Feltovich [4] proposed a new paradigm/concept that sPTB three essential elements (cervical remodeling, myometrium activation-preterm labor, decidua-preterm membrane rupture/hemorrhage) are inextricably intertwined, all lead to each other. These factors are considered as a possible "phenotype" for sPTB [4, 5], such as those that start with premature activation of fetal membranes leading to PROM vs. myometrium premature activation leading to preterm labor vs. premature cervical remodeling leading to cervical failure, but 25% of sPTB are not associated to any phenotype [5].

Prematurity rate has not declined over the past 40 years, or a small decline was followed by a new increase, and despite significant medical and management strategies advances, it has a continuous slow rise, with high offspring morbidity and mortality, affecting 14.8 million babies annually worldwide [6]. Management with actual opportunities of assessment and medical/surgical procedures—elective, urgent, and/ or emergency, consuming a substantial portion of the health budget [7, 8] is the aim of modern obstetrics/perinatal medicine societies, being imperative to improve medical understanding of normal/abnormal reproductive tissue structure and function, and how these tissues interact at cellular and biochemical level, and to act accordingly. This chapter focuses on cervix uteri involvement for sPTB prediction and prevention/ delay through cervical abnormal remodeling identification by non-invasive novel approach imaging techniques.
