A baby can be born at anytime, but in order to have a chance of survival the baby needs to be at least 24 weeks and then the odds are only at 50 percent. There is not a set time for the survival of a baby born early. A premature baby is one that is born before the 37th week of pregnancy. When you are between 23 and 26 weeks pregnant every extra day in the womb increases the chance of survival by 2 to 4 percent. Babies born earlier than 23 weeks do not have much of a chance for surviving.