She started regressing In age and while she did, she gave you the ring while restricting a bit of use with it,
"take the ring, it's yours now. Wait a tick while I bind us together, you may not abort my comeback with the ring or anything else, you may change everything except for YOU must carry me... You may not regress me further than I want because I want to be back when I want to, not you! When you will give birth, I want to hear you scream and come when I want to in the world so, any drugs that doctors will prescribe you will be uneffective on you. rejoice! I want to be born later than term, about after two years after I'd normally be born and I also want to come back in a classic position, you are lucky! And I want to be fed with your milk!" she explained as she regressed, by the end, all she said was with a baby's voice
as she was finished regressing to a new-born's state, you started aging, then, your hands got slender and softer, soon, your arms and shoulders followed, narrowing and being pulled back until you started feeling your bottom part changing. Your ass started trembling and becoming tight and round as your hips cracked larger and your legs got feminized, not a single hair anymore.
It was then that you noticed your teacher's newborn form was forming a placenta around her, then, you thought "why is that hovering and why does that go toward my penis?!"
then, it accelerated to hit real hard your urethra and enlarge it to become a slit, then, softly, your placenta entered your slit and started settling in your new-formed womb. Then, the last changes occured and your vagina and the rest of your body finalized themselves. Your belly decreased in volume to become one of a five months pregnant woman with twins. The other hadn't been destroyed in the swap.