Thank you for considering this issue.
To me, the question isn’t about justifying timelines, but rather: Do we trust women to make decisions about their own lives, or not? The CDC reports that in 2013, the last year for which they have published statistics that I could find, only 1.3% of abortions were performed at ≥21 weeks’ gestation; I assume the number would be significantly lower by 26 weeks. What compels the rare woman to seek an abortion at that time? If she simply did not want to have a child, and safe abortion were physically and financially accessible earlier, then why wait until you are visibly pregnant and the procedure is more fraught, and less safe, and less available? From what I have read, the reasons usually come down to discovery of non-viability of the baby; the mother’s health; or lack of earlier access. But here’s the thing…I don’t know. I can’t know, because I don’t know that woman and her circumstances. But she does, so I must conclude that she is better equipped to make decisions for her own life and family than I am. I have to trust her, because I know I deserve to be trusted to make those decisions for myself.