Thoughts on HCG levels…

My HCG level was 1270 at 5weeks 6days, but then only rose to 1372 48 hours later at 6weeks 1day. I’ll go back for another test at 72 hours from the second test. If it’s still rising slow I think I can assume a miscarriage. I did read that levels can take longer to double after 1200. Any thoughts here?