Measuring Small, Low Heart Rate

So I was diagnosed with a Subchorionic Hematoma at  4 weeks, last week at 7w0days I had an ultrasound, I was measuring perfectly and there was a heart rate of 98bpm. Today at 8w0days the baby is measuring 6w3days with a heart rate or 85bpm... Has anyone had this happen and have a healthy pregnancy? I'm trying to stay positive as i miscarried in September at 9weeks... Tia!