Babies should hopefully be born at the right time when they've fully developed to be the healthiest however sometimes babies can and do get born early which leads to complications.
But most times a baby born at 35 weeks can breathe on their own just fine although some might need to be in the NICU and need breathing assistance until they become full term.
Anytime a woman goes into labor and gives birth to the baby before 37 weeks the baby is a premature baby and sometimes complications can happen.
Babies born at 35 weeks or before 37 weeks are premature and although they may not always be admitted to a neonatal intensive care unit (NICU), they are still at risk for more problems than full-term babies would have.