I'm ~4 weeks pregnant via IUI. My initial HCG levels were 131 last Thursday, which the nurse said was very good (they want them to be 50-100). They should have quadrupled by today to 524, but were only 471. She said this indicated that something wasn't right; either there were two but now there's only one, or that it wasn't going to be a "good" pregnancy. I've done a little research online (which isn't always a great idea), and felt a little better to read that a 60% increase every 48 hours was considered normal, but I'm still very worried. My husband and I have been trying to conceive for ~2 years, and this was our 2nd IUI (the first one didn't take). I go back Wednesday for another blood test. Has anyone else had a similar experience?