When the uterus begins to contract again after the birth it shrinks in size. This process involves the muscles in the uterus shortening or 'retracting' to achieve this. Most women are aware of this contraction, feeling mild to moderate discomfort (or cramping) at this time. Others will not be aware of any discomfort because their full attention is with their beautiful baby or they are possibly too exhausted to take anything in!
Several mechanical processes need to take place simultaneously during the separation phase to help the placenta fully detach from the wall of the woman's uterus and to control the bleeding from where the placenta was attached.
These are:
Uterine contractions and cramping
Placenta detaching
Blood flow being tied off
Uterine contractions and cramping. The uterus needs to contract to allow the placenta to separate. As the uterine muscles contract and retract, the uterus tightens up and becomes smaller and firmer (similar to watching a balloon slowly deflate). The shrinking inner walls of the uterus cause the placenta to start to 'shear off' the wall of the uterus or to separate. The placenta is about the size of a dinner plate and the inner surface of the uterus contracts down to about the size of a bread and butter plate, making the placenta detach.
Many women experience cramping pain during the 3rd stage, so keep the heat packs available. Your labour is not complete yet and the heat can help soothe the discomfort.
Placenta detaching. As the inner wall of the uterus shrinks, the centre of the placenta starts to detach or lift off the wall of the uterus. This tears the blood vessels that were providing the uterus and baby with its plentiful blood supply. A small clot forms in the middle of the placenta, between the placenta and the uterine wall. This clot aids the separation process as the placenta continues to detach, lifting further towards its outer edges.