What is a chemical pregnancy?
A chemical pregnancy is just a MC that occurs earlier in the pregnancy... it is what a blighted ovum would be if the MC didnt occur for a few more weeks or was delayed(sac formed without the embryo)... In lots of the cases the chemical pregnancy isnt even noticed as it occurs when the womans period was due or shortly after so the woman might not even notice and may not have known she was pregnant...
After the pregnancy is confirmed by US or increasing hCG levels a chemical pregnancy would be ruled out... as far as the risk fro MC in general it significantly drops after 12 weeks... thats why most dont tell too many ppl if any until after the 12 week mark