A few things can happen.
A) She might become impacted which means she cannot lay the eggs. This can lead to her death and will mean the death of all babies.
B) She will lay the eggs and die from all of the effort.
C) She may suffer, like you said, being stunted from early breeding which would likely be permanent.
D) She may just pull it off with no complications.
All in all, it's risky for many reasons. How early are you talking here? There are general size/age guidelines that will give you an almost sure idea if she is ready to breed or not.
Others may be able to give first hand experiences on the subject. I'm just telling you what I've heard and learned over time....