Understanding Elevated hCG Levels in Early Pregnancy

Question
I am 27, this is my first pregnancy, we know the conception date is 12/14/05 (we had IUI with an hcg trigger and used follistim injections to concieve). My question is about my hcg levels. We had them tested at 13dpo and again at 15dpo and they were 159 and 378 respectively. I know that is is higher than normal and I wondered if this might indicate multiples. We know we had 2 follicles that were over 20mm and 1 that was 17mm. We have an ultrasound scheduled for next week and I just was wondering because all my doctor will say is "let's see what's going on in there".
Any thoughts?
Thanks.

Answer
The range of HCG values at 2 weeks from conception (4 weeks gestation) is 500-10,000. Your values of 590 and 378 are not high but are a bit low for 4 weeks pregnancy. (Remember, we count a pregnancy from the first day of your last period, not from the day of conception). HOwever, your values are doubling nicely and I would repeat the HCG test in another week. A sonogram less than 6 weeks gestation will only usually show an empty gestational sac. I would suggest that you take a sonogram at 6 weeks gestation (4 weeks from conception). After 6 weeks, we usually see a fetus and a fetal heartbeat.