In other words: Consensus exists (if not unanimously), and the consensus is that uterine implantation is the moment at which pregnancy begins.
We presented that description to the senator’s office, asking if he wanted to clarify or moderate his statement. Brooke Sammon, the senator’s Deputy Press Secretary, told us that “Senator Rubio absolutely stands by the comment.”
There’s a blurry line between “pregnancy” and “life” in this discussion. When we asked ACOG if the two were interchangeable, we were told that the organization “approach[es] everything from a scientific perspective, and as such, our definition is for when pregnancy begins.” On the question of when life begins, then, the scientific experts we spoke with didn’t offer any consensus.