trans | T as birth control?

I have seen several posts around lj now that either state, ask or imply that being on T can be used as a birth control method.

I get that some people have their ovaries "shut down" and that it stops one's period (ymmv).
However, I don't consider being on T as a method for not getting pregnant while having PIV sex with non-trans guys. And I would never suggest to anyone that it was.

What are y'alls' thoughts on this topic?

x-posted