No they won't my 4th I was delivered due to pih at 37 and she spent 2 weeks in scbu. She was a good weight at 7.4lb but still couldn't feed on her own and had other issues. My first I had pih then hellp they had me in hospital 3 months. At 39 w they delivered me she was 8.9lb they knew she was gonna be big before but wouldn't deliver me till I nearly keeled over. My 3rd was 5lb at 32 weeks and 9.4 lb at delivery at 38 weeks. Babies weight has nothing to do with breathing and feeding and temp regulation ability. Some 3 lb babies don't need oxygen others need everything. Same goes for 5-6 lb babies. A full term baby can struggle hence why they don't do non medical inductions or sections before 39 weeks