Beyond that until the late second trimester, a fetus can not survive outside the womb on its own, and would take a quantum leap in technology to change that. (religion.blogs.cnn.com)
By week 24, your baby has a 25 percent chance of surviving outside the womb, thanks to the production of white blood cells and the partial development of baby's lungs. (pregnancymagazine.com)
You are correct about babies as young as 21 weeks surviving outside the womb. (religion.blogs.cnn.com)