And this thread is a pretty good indicator of how the abortion argument often goes haywire. It is so often argued from the perspective of "My opinions are correct," which is just what is going on here.
But consider this: Is it the government's job to decide who among us is morally "correct"? Abortion is also a religious issue; do any of us want the US Federal Government to decide which religious view to take? To me, that sounds like the opposite of everything our country was based on.
Neither the US nor any State or regional law can criminalize abortion without first establishing personhood; that is, asking "At what point is this being considered a 'person' in the legal sense, and allowed the full protection of the law?" There are people in this country whose ethical, ideological, and religious views tell them that that personhood begins at the very spark of conception, and there are others who believe just as fervently that that same personhood does not begin until the baby emerges naturally from the womb, and every opinion falls somewhere along that timeline. If we allow Congress to pick one day out of nine months to say "NOW it's a baby!", whatever they choose they will be stepping on the religious beliefs of at least many, and probably most, of the people.
I hope everyone here agrees that the job of the American government is to guarantee the freedoms of as many people as it can. That means they should not only refrain from infringing on our freedoms themselves, but it is their job also to protect us from someone else, some third party, from infringing on those same freedoms. That is, in fact, the technical difference between civil liberties and civil rights; the former restrict the government while the latter are freedoms that the government is tasked to protect. You can look all of this up in any US Government or Poli Sci textbook.
So by following the line of thinking from step to step, we've now established that the government shouldn't force any one stance on us by picking a day for personhood. What, then, should they do? Their job should therefore be to protect the freedom of each individual person among us to make the moral, ideological, and religion decision according to our own conscience. They must guarantee our civil liberties by not outlawing abortion ever, but also to guarantee our civil rights by preventing anyone else — namely, the States — from doing that either. That's their job. That's why we have a Federal Government. Constitution says so.
I realize many of you can feel your blood boil while reading that paragraph, but you have to remember that yours is not the only view on when personhood begins, and the republic is founded upon the idea that everyone else's views are just as valid as yours.
So, from a Constitutional perspective, the answer to the OP is this: I have my opinions which work for me, but regardless of what they are, I should not be allowed to impose them on everyone else. When we're talking federal law, the government's job as laid out in the Constitution should be to protect our civil rights by preventing States from criminalizing abortion.