Let us assume that Mohammed PBUH before 1400 years ago mentioned the embryology stages from his own mind and of course that will mean nothing for the people at that era because they weren't doctors or highly educated but for us now we know much better than people of that era (1400 years ago).
So please try your best to make a verse in few lines from your own mind that describes the stages better than Mohammed PBUH as we are now in the 21th century.
After that i will see if that verse in the quran was just easy to be authored by prophet Mohammed before 1400 year.
Who said it was from his own mind,there was trade in the 7th century,Muhammed was a trader and with trading comes information,i can see the Sura being impressive in the 7th century though, even if it starts out on the wrong idea that we were made out of clay.