Yeah, it really does differ between babies. My 4th was born at 31 weeks, 5 days and was 4lbs, 8oz and breathing on his own, no ventilator needed. Aine was born at somewhere between 32 and 34 weeks, since she was so small we don't know for sure. She was 3lbs, 12oz. Still no ventilator needed, but she is much smaller than Kaiden was who was younger gestationally. 36 weeks is considered safe, but I'd hope for no less than 38.