This paper deals with a new mechanical birth simulator (BirthSIM). Currently available birth simulators provide manikins that include new-born head and maternal pelvis but they do not produce the movements of the new-born in the mother's pelvis. Furthermore available maternal pelvis do not include interface pressure and are not enough realistic to simulate maternal pelvic muscles. In summary, these simulators do not help students to practice the gestures they should safely use to help the new-born in normal and at-risk situations of delivery. The originality of our mechanical birth simulator, is to provide a system to mimic the last step of the instrumental delivery, to insure a safe training of junior obstetricians and to test new techniques in obstetrics practice. The new mechanical birth simulator is composed of three parts: a physical new-born head and a maternal pelvis manikin, an interface pressure system, and a pneumatic actuator that develops an active resistance. Driven by a computer, the simulator can simulate the contractions, the interface pressure applied in the new-born head and mimic birth complications.