Hcg levels not doubling

sarahrat

I had my hcg checked last Friday and it was 3891, then again Monday and it was only 4654.  It didn't double like it should have so my doctor sent me for an ultrasound on Tuesday.  She said my sac was measuring at 5 weeks 5 days, no fetal pole yet...according to LMP I should have been 6 wks 6 days, but makes sense as some of my cycles can be longer.  What the concern is that my hcg levels did not double.  The nurse did say she's seen this happen and everything has been just fine, but there is a chance I could miscarry.  So I'm having another ultrasound next week to make sure there's growth, but no more blood work.  Has anyone else had this happen with their levels not doubling and baby is fine?