It's an old way of identifying when life begins. It's the reason we have birthdays.
I think it's funny when some smarty pants kids at 20 years old will walk into a bar and ask for a drink. When the bartender asks for identification, the person shows how old he or she is, the bartender refuses, and the kid says, "Yeah, my birthday says I'm 20, but I've been somebody since I was conceived....
21 years ago....so I'd like a beer to celebrate." [when the drinking age minimum is 21]
The government does not recognize humans starting at conception. It's too difficult to measure and document and maintain, so overall a birth certificate identifies and recognizes inalienable birth rights....including the right to life. Fetal viability around the 24-26 week of gestation is that grayer area of when it is ethically feasible to terminate a pregnancy through surgical abortion procedures.
One thing that continues to be glossed over is the fact that abortion rates around the world are not diminished from restricting access. They are diminished with full and legal access to contraception and family planning services as well as comprehensive sex education PLUS access to safe and legal abortion.
When women are given the freedom to decide when they can have children or not, abortion rates GO DOWN. They will always be there, but restricting access to abortion only increases mortality rates for women and girls who attempt to find illegal means of terminating pregnancies anyway.
It's the blank-unholy-irony of the abortion debate. Empowering women's autonomy to do exactly what she wants sexually with her body at all times of her life offers the lowest abortion rates across cultures. Not shame tactics. Not restriction. Not austerity. Women and girls seek to terminate unwanted pregnancies in all religions, cultures, ages, socio-economic classes. So changing marital statuses or universal health coverage or anything outside of full and safe legal access to family planning services does little to nothing to lower abortion rates.
THIS is why the abortion debate is truly, ultimately, about controlling women's reproductive choices.