Found this online, hope it helps:
well since i been doing research on fetuses, my girlfriend is pregnant i believe that a 7 month old fetus can survive preterm birth because of development, so does the 8 month old fetus, but i believe the 8 month old fetus can't survive because it was almost born, i guess.
Personally, I haven't heard of this, and can't find it in any of the medical textbooks I have.
An 8 month fetus has more chance of survival than a 7 month old fetus because it is more developed. The weeks just before full term birth, the baby is working on lung development. Neither than 7 month old nor the 8 month old has full lung capacity development... and actually the 7 month old hasn't even started much on this one.
It really depends on any other complications that arise. If the 8 month fetus has more complications, say because of genetics or trauma besides the pre-term delivery, it would have a lesser chance of survival compared to a 7 month fetus that has little or no complications, either genetics or trauma. Both fetus are at risk for pre-mature illnesses and the normal complications that stem from being delivered early.
In either case, medical technology has advanced quite far in these times. Both fetus have a chance for survival with various treatments, medications, machines, and procedures, depending on the needs of the preemie and the stage of development, as well as post-partum circumstances that arise. It is still true, however, that the further along you can carry the baby, the better chance of survival it has because it has been able to be more developed. This is why, if you are too early, and you have true labor pains, the doctor will give you medication to stop the labor and thus give the baby more time to develop in utero.
