Because it's a lie. It's not even a fetus until week 9, it's a clump of germinal cells or an embryo. It has the basic germinal beginnings of some organs, including the heart, but not all. The heart is basically a bulge, it is not a fully formed organ that is circulating blood in the manner we know of, even though rudimentary beating is taking place. There is no vasculature.

Most organs are "buds". This includes the brain and the lungs which are also part of the circulatory process.

There's no way they are viable outside the mother's body.

My biggest problem with the "at the first heartbeat, it's a baby" mantra: if you go to Wikipedia, most of the embryonic pictures they have are from ectopic pregnancies. Fairly well past 6 weeks. Ectopic pregnancies are not viable and they kill. A whole lot of ectopic pregnancy terminations are emergency situations. Lots of times, the medical crisis is how the woman found out she was pregnant. Your stupid heartbeat law to save babies that will die anyway is sentencing those women to death. Agonizing, painful death.

One in 50 pregnancies is ectopic.

How do you claim moral superiority by risking one life to save another that cannot be saved? Where do you get off calling people murderers for having to make hard choices? Are you not just as guilty of murder by supporting and advocating this insane law? You've sentenced people to die. How are you not a murderer too?