[ceptimus]

I don't think relativity is that important for earth-based births and deaths. All people on earth can use a common universal time, such as the one transmitted by GPS satellites, and can agree with each other about the timing of events down to microseconds.

It's not possible to time stamp the exact moment of birth, death, or conception to a resolution of even one second, so the shared clock time is already about a million times more accurate than is needed.

Even an alien flying her spaceship past earth at close to light speed would worry more about whether person A has really died yet and person B really finished being born, than she would worry about how her perception of the order of the the events might differ from that of an earth-bound observer.