Implanting at birth, activating at a suitable marker point after puberty (a sensor which monitors normal progesterone levels would actually be fine for this) and de-activated when a women wants to conceive.
It'd be the most important bit of social policy in human history, seeing as how reproductive control and economic outcomes for women are very closely linked.
Something like this applied en masse in developing nations would also directly save a lot of lives.
<puts the tinfoil hat on>
And then you need to get a deactivation code from the government to disable the implant to conceive. So the government gets the power to decide who can have children. This concept sounds very enticing and I think it would actually be a good idea,if not for the fact that I don't think anyone should hold that power over other people, even if it's in best intentions.
It'd be the most important bit of social policy in human history, seeing as how reproductive control and economic outcomes for women are very closely linked.
Something like this applied en masse in developing nations would also directly save a lot of lives.