Abstract This hypothesis is accepted for iposter presentation at the RCOG world congress 9-12 June 2021. It is also, accepted for publication in the online World Congress edition of the BJOG journal. This submission is 3D-animation for the hypothesis.  https://www.youtube.com/watch?v=0e00RQFdj6w Background: The smooth muscle of the uterus during pregnancy presents a unique circumstance of physiological mechanotransduction because the tissue remodels in response to stretching imposed by the growing fetus, yet the nature of the molecular and functional adaptations remains unresolved. (1) We hypothesize that the exponential uterine wall tension (EUWT) (2) is the functional component of the uterine mechanotransduction and the intrinsic myometrial cell character (IMCC) is the molecular component. IMCC enables the uterus to control its function autonomously and intrinsically secondary to tension change. Where high tension induces relaxation and low tension induces contraction. (3-5)  Objective: To answer: What is the primary function of the cervix during pregnancy?  What is the mechanism that initiates labor when the cervix loses strength? Methods: Review the evidence-based that supports this hypothesis. A 40-second 3D animation supporting the hypothesis was developed in conjunction with Houston-based Baulsen Medical Company.  Conclusions:    Uterine wall tension (UWT) is created and maintained autonomously through a complex interaction between the gestational sac, the uterus, and cervical support. UWT followed an exponential curve, with results increasing throughout pregnancy, and later preterm birth was associated with a lower UWT.(2)   Pregnancy is a balance between two opposing interactive forces, mechanisms, and systems. The first force, EUWT, is the inhibitory system that maintains pregnancy, through a stretch-dependent (mechanotransduction) mechanism, in addition to direct relaxants.                                   The second force is the stimulatory system, which terminates pregnancy by transforming the cervix into the lower uterine segment through the TYVU pattern. Both the inhibitory and stimulatory systems are induced secondary to exponential uterine wall tension (EUWT) mechanotransduction and direct progesterone/estrogen stimulation.  Autonomic two-system interaction secondary to light-dark cycle modulation divides gestation into five phases: growth, maturation, transition, parturition, and involution.  Maternal cortisol modulation of the inhibitory system, and melatonin, and oxytocin exerted on the stimulatory system is synchronized and synergized, making the cervix lose its strength completely at the end of the maturation phase, secondary to its transformation into the lower uterine segment, which signals EUWT failure and initiating parturition. The clock metering the duration of pregnancy has been suggested to consist of two interacting timers; an interval timer measuring the overall length of gestation, and a circadian timer defining when within a 24-hour cycle birth takes place.(6) The pregnancy interval and circadian timers are achieved by a single mechanism, EUWT failure, secondary to the complete loss of the cervical resistance nocturnally.   Gestation is Genetically Controlled through the Complex Interactive EUWT components which include the paternal side as well. The Creation, the Autonomic Maintaining, and eventually the Autonomic Termination of the EUWT through light-dark cycle modulation make Gestation an Autonomic Cycle with a Constant Interval and Circadian Timers. Malfunction of any interactive EUWT component terminates the Gestation prematurely or post-term or leads to Dystocia in Labor.