system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How can a woman create a fully functional baby in nine months but can barely heal a broken ankle that’ll never work again properly?
gpt
Because embryogenesis is a series of unimaginably complex and carefully sequenced construction tasks involving cellular machinery that is permanently switched off after the work is done. There's little room for error and everything has to happen right the first time- mistakes manifest as birth defects or failed pregnancy. 

After that, our body's own healing mechanisms are responsible for injury recovery, which are not meant to build human body parts but to repair them. It's like trying to repair a building after it's already built- you'd need to disassemble existing structures to replace what's broken. The body can't do that. 

We're complex creatures, and lack the ability to regenerate our bodies in part because a broken bone isn't the death sentence for us that it is for many other animals. We can still survive even if our body doesn't always heal perfectly.