Labour Delivery Model - Six Development Phases Demonstrating Cervical Expansion Dynamics | Shows Fetal Head Positioning Relative To Ischial Spine

This series of Labour Delivery Models consists of six development phases and each part shows a state of prenatal cervix and birth canal. The whole models demonstrate the relations between the scope of the expanding of the orifice of cervix, and the range of cervical tunnels, as well as the relation between the position of the head of fetus and the square of ischial spine.
*The orifice of cervix has no expanding, and the cervical tunnels haven't disappeared at all. The positional relation between the head of fetus and the square of ischial spine is -5.
* The orifice of cervix has expanded 2cm bigger, and the cervical tunnels disappear 50%. The positional relation between the head of fetus and the square of ischial spine is -4.
* The orifice of cervix has expanded 4cm bigger, and the cervical tunnels disappear absolutely. The positional relation between the head of fetus and the square of ischial spine is -3
* The orifice of cervix has expanded 5cm bigger, and the cervical tunnels disappear absolutely. The positional relation between the head of fetus and the square of ischial spine is 0.