How common is a blood clot after using methotrexate to treat an ectopic pregnancy?

[Goodlife]

Good afternoon,
My wife recently had an ectopic pregnancy. She was treated with methotrexate, and her numbers continued to rise until the second shot, after which they fell very quickly (over 70% in a week).

On the day before we found out how far the numbers fell, my wife started feeling a bit of pain in her right side (the ectopic side). It hasn't gotten very bad (yet) but it's uncomfortable. Accordingly, she went to the doctor and got an ultrasound of the area, and they said the ectopic was gone, and a blood clot was there in its place.

How common is this? Does it resolve on its own, or is it something that has to be removed surgically? My wife was planning to go into surgery for the ectopic, but now that she knows the pregnancy hormone is falling so far, she's not sure any more about the surgery.

Thanks for you help!