I was reading a fetal medicine textbook, when I came across this surprising statement:
"Yet today, it is not uncommon for fetuses to be born at ages equivalent to 19 or 20 embryonic weeks and survive." (Collins, P.26)
Babies surviving at 19 weeks?
I don't want to invest too much in this statement. But I have found that medical textbooks tend to repeat conventional wisdom rather than actual scientifically tested notions. So the idea that viability is around 20 weeks is just something that "everyone knows".
I think this statement could bear some investigation.
Patricia Collins. "Staging embryos in development and the embryonic body plan".
Fetal Medicine: Basic Science and Clinical Practice
Charles H. Rodeck, Martin J. Whittle, Ed.
Elsevier Health Sciences, 2009