7 months ago, I had a history of fetal loss. After that, my menstrual cycle returned to normal. My cycle is 30 days, and it ends after 4 days. On December 18, I had a period, and then on January 17, my period was due but was late until January 25. I used a pregnancy test strip and saw one faint line and one unclear line. I went for an ultrasound, and no gestational sac was seen. On February 1, I had another ultrasound, and the doctor said there was a gestational sac, but it was still unclear, so I should keep monitoring. The doctor calculated my pregnancy at 6 weeks, but the gestational sac is still unclear, and I am discharging a little bit of black blood. I told the doctor performing the ultrasound about it, but the doctor did not say anything. Doctor, may I ask if black bleeding at 6 weeks pregnant with an unclear gestational sac is harmful or not? What is the reason for this black bleeding? Thank you.