I haven’t personally went through this, but I know many woman that have. It can happen for a variety of reasons. Some are “normal” in a sense, but others are because of abnormal causes.
One reason could be sex (if you had it before the bleeding). There is a ton of extra blood flow going to your cervix right now and it can get irritated very easily. Sex can cause irritation and bleeding sometimes.
Another reason I know of is a subchorionic hematoma. It’s basically a blood clot under the placenta. What happens is the placenta pulls away from the uterus in some spots (can be toward the end of the placenta or in the middle of it. This causes the blood clot. If it is at one of the ends, it can cause bleeding. If it’s in the middle, it may not cause bleeding at that time, but could at a later point or it could be reabsorbed during the pregnancy. Subchorionic hematomas are abnormal and not very common, but once diagnosed (through an ultrasound) they can be cared for (everything from limited your exertion, to bedrest, to medications) depending on the size and location of the subchorionic hematoma.
I have a subchorionic hematoma that is under my placenta in a way that it has not caused any bleeding at this point. Every time I have an ultrasound, they measure it to see if it’s changing. They found it when I was 5 weeks along, verified it was still there and hadn’t really changed any at 9 weeks along and then again at 12 weeks. They won’t look again until my anatomy scan at 23 weeks unless I start bleeding.
When I talked to my OB about it, he said that if I start bleeding, to come in so they can check the baby. As long as the baby still has a heartbeat, they will do everything they can to keep the pregnancy going. He told me that he once had a patient with a really bad subchorionic hematoma that bled quite a bit. He said she got to the point where she would start bleeding and have to get blood transfusions because her blood counts would get low, but the baby stayed alive throughout it all and she made it to term and had a healthy baby.
I feel like I’m rambling now. Hopefully you’ll get some answers on Monday about what they think caused the bleeding and more recommendations for you. Sometimes they really don’t know what caused it. It’s great that it stopped and I hope it doesn’t happen again for you.