Understanding Bleeding During Early Pregnancy: What to Expect

Question
I had a sonogram to date my pregnancy last week.  The sonogram showed good fetal activity, we saw the heartbeat and the pregnancy was dated at 6w1d.  The image also showed a small dark area outside and seperate from the sac, which the tech indicated was likely an implantation bleed.  

My doctor has ordered a second sonogram, two weeks from the initial sonogram, to check on this situation.  I've had no spotting at all.

My questions are, how common is a bleed at this stage in pregnancy?  And how likely is such a bleed to complicate or terminate the pregnancy?  

Many thanks!

Answer
As long as the hematoma is not within the gestational sac, it probably will not interfere with the fetus or with the pregnancy. Often we see a "subchorionic bleed" in the folds of the placenta as it is being formed. This usually disappears on its own; I would repeat the sonogram in a couple of weeks to see if the clot has disappeared. As long as you are not having any bleeding, you should not worry.