I hav low iron and just found out im around 5wks. my bowel movement was near black..is that normal?

Hey ladies and gents! i'm a new mom to be around 5wks along. i had low iron before i became pregnant and i dont want it to get worse. i've been taking my prenatals and this morning i realize that my stool was extremely dark near black. can someone tell me what this could mean. im EXTREMELY worried, should i be?? Also can low iron cause you to miscarry?