Most likely ok, but
Spotting during pregnancy
is common--often due to minor bleeding as a result of repeated trauma to the more vascularized-cervix
during active relations etc.
.If small bleeding occurs and the blood stays in the vagina cannal for long period..I.E. Overnight...The acid in vagina can turn blood dark-brown. If no other symptoms, u r likely ok. If u r still concerned, consult doc. Congrats n good luck.