20 weeks, small bit of thick dark brown/black discharge on underwear once every 2/3 days, tested discharge and found not to contain blood, what is it?

Good Q for OB: Have you had any problems with the pregnancy, especially the placenta? Have you undergone an amniocentesis? Are you having any unusual bowel activity? What tests did the doctor do on the discharge? Are you leaking otherwise clear fluid or greenish fluid? It would help to have that information so we can give an answer. Thanks for asking.

Well: Just wondering about testing it for blood. If it looks like it might be blood and coming out of the vagina it probably has some blood in it. May increase with sex, may benefit from a drug called Prometrium (micronized progesterone) to help decrease substance but there are few options of vaginal discharge and none i can think of that look like blood but arent. Good luck.

Bleeding in pregnanc: You may have a placenta previa which is causing spotting , folliwed by dark brown blood. Have the ultrasonographer check the location of the placenta at your next visit.