From the article:

Blackmun’s ruling included a few elements that gave precedent to Alito’s striking of the decision.

The Right to Privacy regarding abortion is not only not Absolute, but it all hinges upon proving the personhood of the unborn. At the time, science had not progressed to a point experts would weigh in on such an idea of the personhood of the unborn. However, has that been proven, according to Blackmun’s opinion, the woman seeking an abortion would “no longer be alone in her personhood.”

In his original opinion on Roe, Blackmun says, “If the suggestion of personhood is established, the appellant’s case, of course, collapses.”

https://www.thegatewaypundit.com/2022/06/reversal-roe-possiblity-designed-court-1972/