First priority: I should be able to clip my fingernails and have moles and warts and tumors and parasites removed. Bodily autonomy is a core foundation of liberty and freedom.
Also First priority: Human beings, especially the weak and defenseless ones, must be protected by society and law. Humans get equal protection under the law - also a core foundation of liberty and freedom.
So when does the reproductive cycle create a human, deserving of equal protection under the law? Pretty much nobody advocates extending the status of personhood to a sperm, or an egg. Few believe a fertilized egg or multicelled blastocyst is a human. As the thing grows and matures, more and more people cross the "okay it's a person now" line. Every stage crossed, brings more and more into the "it's a person" camp: A beating heart, the ability to feel pain, brain activity, indications of having a sleep pattern, reactions that indicate familiarity to certain sounds. By the time of viability (the ability to survive outside the womb), pretty much everyone has joined the camp. You can find some, here and there, who believe a woman should have a right to abort her born and independently living child, but probably in similar numbers as those who believe spilling seed is mass murder.
There should be room for exceptions, like the 14 year old who escapes from her evil father, in the 3rd trimester carrying his child, a child that will not survive for long and will likely kill the mother during birth.
God drops hints that can be interpreted in various ways. He doesn't settle the matter for us. The church does what it always does in the lack of clear and unambiguous revelation - it's best.
In such a situation, it makes sense to let the states (or the people), make up their own minds. Folks of similar views can go live amongst others of similar stripes, if it's that important to them. So let Cali and Colorado be on the late end of things, and let Georgia and Mississippi be on the early end of things, and everyone else can argue about weeks, and yell in all caps, and crowbar as much emotion or reason into their arguments as they wish. And they can vote in their states, and the strongest voices will win in that state. And folks can argue about jumping states for abortions. That's better than the federal government telling everyone what to do.