Sequoia, by natural third stage I mean no syntocinon or syntometrine. If you're already on the drip (syntocinon) you wont have the shot of syntometrine, which is often just given without asking into the woman's leg to expel the placenta quicker and prevent bleeding (as they will tell you, if you've had a normal birth then your risk of bleeding out is low, higher with inductions). A natural, physiological third stage is allowing the placenta to come naturally without immediate clamping and injection of synthetic oxytocin - a natural third stage is one without interference. Its like saying a natural birth is a birth where the baby comes out of the vagina - when we know there can be so many unnatural (and sometimes necessary of course) factors than that