Note very carefully the rights weighing that occurred in Roe–and even that by Alito in his draft, do not actually address the rights of the fetus. This is because that opens a constitutional black hole, from which nothing might escape. The reason the Roe court could not simply conclude that abortion is unconstitutional because it violates the fetus’s right to life, is there is no constitutional, traditional, or legal history affording the fetus any personhood rights at all in 1972. Some States have been deliberately attempting to establish the legal concept of “fetal personhood” ever since, but that is a movement that essentially exists solely as a reaction to Roe.
It would have been essentially crazy, legally speaking, for them to have invented fetal rights out of thin air. Additionally, it would have put the Justices in the position of deciding at what point in human gestation a fetus inures those rights. As you can see, that isn’t a good place to be legally, and would almost invariably devolve into a theological debate, which the Supreme Court isn’t supposed to be involved in.
Ruth Baden Ginsburg in her criticism of Roe, wishes that if you were going to enshrine abortion as a protected constitutional right, to have done it out of the bodily autonomy rights of the woman. There is actually significant constitutional jurisprudence about bodily autonomy. That is not the route that the Roe justices went, they were frankly much more concerned about the privacy implications of the Texas law, and the rights of the States. The bodily autonomy rights of the woman, and any theoretical rights of the fetus, just weren’t a significant element of their deliberations.
FWIW–if the court held the mother had a general right to an abortion on grounds of bodily autonomy (which is actually a well-supported right straight out of the rights conferred in the constitution), and concluded that the fetus has “some rights of personhood”, the conclusion would not automatically have been that the woman could not have gotten an abortion. The traditional way to handle competing rights at law is through “rights weighing”, which gets complicated and technically precise, but the competing rights would have to be spelled out in very specific circumstances with specific constitutional justifications involved.
While I don’t agree with his conclusions, Sam Brownback once said that under the law, anything that exists in an uncertain state between property and person, creates serious legal / constitutional issues. His examples were chattel slaves and fetuses. He is right largely that that core conflict creates a very sticky constitutional issue. The only way the court could ultimately resolve the competing concerns of property and humanity for slaves, was to come down firmly that slaves were not people, in Dred Scott. That decision was monstrous beyond belief and is frequently cited as the worst Supreme Court decision in history. However, the logic of Dred Scott makes sense even though it was bad law–if you want to really settle slavery, you cannot have jurisprudence that quibbles on if a slave is a person or a thing, if they are a thing then slavery is logical and legal and makes perfect sense. If they are any kind of person, it can never make legal sense under our constitution. The pro-slavery justice behind the Dred Scott decision realized that, and simply made a horrifically unconstitutional ruling in favor of slavery. Note–such behavior is historically normal for the Supreme Court, a noxious institution that only rarely has been governed by forbearance and integrity.