Protected with multiple layers.
The fetus is protected by the:
- Amnio-chorionic membrane.
- Abdominal muscle wall.
So the fetus has three layers of protection.
A fetus receives from the mother everything it needs of nutrients, oxygen... A fetus can even here sounds however it cannot see anything because light cannot reach there. Light is the only thing that doesn't reach the fetus.
However 1400 years ago the Quran said that the fetus sits inside three darknesses:
[Quran 39.6] He created you from one person, then made from it its mate, and brought down livestock for you eight kinds in pairs. He creates you in the wombs of your mothers, in successive formations, in a triple darkness. Such is Allah, your Lord. His is the kingdom. There is no god but He. So what made you deviate?
A fetus sits in complete darkness inside three protective layers. Light is the only thing that doesn't reach a fetus. No mistakes in the Quran.
How could an illiterate man who lived 1400 years ago have known that light is the only thing that doesn't reach the fetus?