Thanks Jenny. I posted this over in ttc-land, too...
How's this for clear-as-mud info (from the same page as posted earlier):
Greater-than-normal levels may indicate choriocarcinoma of the uterus, ectopic pregnancy, hydatidiform mole of the uterus, normal pregnancy, or ovarian cancer. Once you have had an ectopic prgnancy, you have an increased risk for another, so your HCG numbers may be monitored more carefully.
Lower-than-normal levels may indicate dead fetus, incomplete miscarriage, or threatened spontaneous abortion. Pregnancies destined to miscarry or to be ectopic (tubal) pregnancies tend to show lower levels (eventually), but often have normal levels initially. Some normal pregnancies will have quite low levels of HCG ˜ and deliver perfect babies.