I thought it was supposed to double within 48 hours? I had bleeding Thursday at 6 weeks so I went to the er and had bloods and ultrasounds, ultrasound sound a sac that was 5 weeks and yolk but no fetal pole yet and too small to get a heartbeat. They doctor told me it’s a threatened miscarriage but he was leaving more towards miscarriage. The doctor I saw today was much more upbeat about my results and said they looks good and within range, but just to come back if I bleed heavily like through a pad in an hour.. I’ve stopped bleeding since Thursday and it’s just been brown spotting. He said it could have been blood that got loose during implantation but was stuck up there and released due to baby growth. My cervix is still closed.