About 34 weeks because the lungs are the last to finish developing
The new standard in the US is 39 weeks.
I would say 36 weeks. I had my daughter at 34 and her lungs weren't fully developed so she had to stay in intensive care for a week bc she couldn't breath on her own. But I had my son at 36 weeks and he was completely healthy
And I'm not going by what the doctor would say I'm just giving my opinion because of experience