Hematoma between the uterus and the placenta

I'm 17 weeks and last night a huge gush of bright red blood game out. My husband rushed me to the ER. They did blood work, pelvic exam and ultrasounds. Both of the blood work and pelvic exam came back fine. During the ultrasound they found that I have what looks like a hematoma between the uterus and the placenta. I'm going to see my regular obgyn today and she'll discuss it with me more, but I was wondering if anyone else has had this and had a healthy pregnancy.