Abstract This hypothesis 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=dyyG-Jhxr7o Objective:  Support the hypothesis that the cervix transforms into the lower uterine segment (LUS) through TYVU and inverted U pattern with its subsequent reversal. Methods: This study investigates the current evidence base that may support Roederer and Mauriceau’s hypothesis (the 1800s), that the LUS is derived from the cervix. (1)   A 40-second 3D animation supporting the hypothesis was developed in conjunction with Houston-based Baulsen Medical Company depicting the mechanism of transformation of the cervix into the LUS and its reversal. Conclusions: During pregnancy and labor, due to the complex uterine system with the presence of fetal resistance, each uterine contraction creates two opposing forces that cause direct and indirect uterine cervical interaction (DIDUCI). (2,3) The first force is a direct force that pulls the cervix upward against the cervical ligaments, causing direct uterine cervical interaction.  The second force is secondary to the first force and pushes the fetus down, causing circumferential cervical stretching and indirect uterine cervical interaction. In the third trimester, DIDUCI causes chronic upward cervical traction, which chronically transforms the cervix cranially into the LUS  through a TYVU pattern (4) with simultaneous pushing the fetal head down through the pelvic inlet.  By the end of the first stage of labor, the cervical tissue disappears completely through an inverted U pattern with complete transformation into the LUS. The cervix regains its full deformed shape instantly after the baby’s delivery due to a reversal of these changes. The cervix contributes to the uterine volume when it is transformed into the LUS. The progressive loss of the cervical strength through a TYVU pattern is secondary to its transformation into the LUS, and it is due to DIDUCI. The cervix keeps its strength to the last fibers, and the U pattern initiates labor.  The TYVU pattern dictates the duration of pregnancy. DIDUCI dictates the duration of the TYVU pattern through the interactive relationship between the uterine force and the cervical strength, and cephalon-pelvic proportion. Unanswered Questions: Cervical integrity is essential for a successful pregnancy, what is the primary function of the cervix during pregnancy?  Loss of cervical strength initiates labor, what is the mechanism that initiates labor when the cervix loses resistance? The answer to these questions is submission no. 0264