Because there literally were no other options worth considering. Lol After confirming he was pregnant, he immediately asked if he could get rid of it. The pregnancy, their child, was definitely a mistake. He never wanted to have children. If it wasn’t for the doctor strongly advising against abortion, he would’ve gotten one.
You just said it yourself if it wasn't for the doctor strongly advising it. Therefore if he still chose not to listen to the doctor he had a option to abort it. Wether it was 1% or whatever a part wanted the baby or else he would have said screw the doctor. Other omegaverse do it. Only difference in this one is the author choosing how they want the story to go but realistically he could have still aborted as a option. You can terminate a pregnancy at any stage in life. He felt judged we see he has a issue with being judged therefore he chose to want to have the baby.

Also why are we calling your kid low key a mistake bro... Don't do that talking about was no other option... There was but a part of you really did want this baby so don't low key call him a mistake :/