During labour the cervix or the neck of the womb has to open to make space for the baby. In the first stage of labour the cervix opens which is known as dilation. It needs to dilate to 10cms before the baby's head can pass through.
In the second stage of labour the baby passes down the birth canal, into the vagina, and is expelled from the mother's body.
In the third stage of labour the placenta passes down the birth canal, and is expelled from the mother's body.