I have seen very few Christians who were all that certain that fetuses go to heaven...especially not Calvinists. I'm not a Calvinist.
It's about knowledge vs belief, I suppose.
Have I used the fireman analogy here yet? Probably...but I'll break it out again here anyway.
We have two adjacent apartments on the fifth floor of a building. In both apartments, at the same time, we see that a man has tossed a woman out of the window. Both women land at the same time, and both live and are without injury. One man is hailed as a hero. The other is arrested, tried and convicted for attempted murder.
What's the difference?
Knowledge and intent on the part of the men.
The building is on fire. The 'hero' is a fireman who has tossed the woman into a huge rescue air bag, saving her life. His intent was to save her life, since the window was the only way out of the building.
The next door neighbor wasn't paying attention to the fire, his lack of escape routes or the airbag; he was just trying to kill his wife. However, she landed in the airbag, too, so instead of killing her, he saved her.
According to the logic of 'fetuses go to heaven,' both men should have been seen as heros, right? After all, if the fireman knew what he was doing and why, should it matter that the other guy was motivated to murder, not lifesaving?
It doesn't MATTER whether innocent foeti go to heaven or not. We don't KNOW that they do, so we can't use our belief that they might as an excuse to kill them. GOD knows...so He, like that fireman, can do what He wants. He KNOWS where they are going. We don't. Indeed, I rather doubt that many, if any, women who want abortions get them because that's the way to insure that their babies go to heaven.
Not to mention that murder is rather against the rules, no matter where we think the victims may spend eternity.