HCG levels going down and then back up? What causes this?

[buko]

My friend was spotting a bit around 4-5 weeks and then started bleeding a bit more like a period, so she suspected a m/c. Had an u/s at 5-6 weeks and they didn't see much, but of course, that's still early, especially of she was closer to 5 weeks (not 100% sure of dates, but should be a range of 10 days at most). She bled more and more, like a heavy period, for a couple weeks, and is down to spotting. So sad, she had a m/c, right?

Here's the funky part....

At the time of the u/s (5-6w), they got an HCG level-- 1880.

5-7 days later, they took another level-- 1600. That surprised me a little, as I would have thought it had dropped more significantly (esp with all the bleeding), but what do I know?

Then, 8 days after THAT, her HCG is 2400?

I don't want to get her hopes up (her MWs want her to get another u/s on Monday, which makes sense to me), but the only thing I keep thinking is that she might have lost a twin? It seems to be pretty common (has happened to two good friends of mine, and the other twin was fine). Just because it seems the levels didn't drop as quickly as I'd think, and then rose...? Not by a huge amount, but significantly (50%)?

What other explanations could there be? Do levels ever rise even after you've passed what seems like tissue? At this point, she is or would be 7.5-8.5w, if that helps.

[dayiscoming2006]

I think it's possible she could have lost a twin. It's good she's getting another ultrasound.

[etsdtm99]

It is possible she lost a twin - but it is also possible that it could be an ectopic pregnancy or a molar/partial molar pregnancy.. or an incomplete miscarriage.   there is no harm in hoping for the best, but it doesn't really sound good with such a slow rise.. 
 

[buko]

I'm guessing it's not an ectopic, only because when she had a previous u/s, they saw "something" in her uterus and nothing in her tubes. Could you explain why you think this pattern might indicate a molar pregnancy, though? It was my understanding that one of the usual hallmarks is super high HCG levels, which she definitely does not have...

I can see an incomplete miscarriage, though the significant (if not incredible) rise in HCG still surprised me.

[etsdtm99]

What i've read about molar pregnancy is that it is not terribly predictable, it can be high or low/slow rising HCG levels and fast or slow growth, it can also cause bleeding .. also, i was told that there being something in the uterus at 5 wks does not rule out an ectopic pregnancy.. esp. with bleeding and other 'off' symptoms/numbers again.. am i reading that right that she went from 1600 to 2400 in 8 days ? .. 2400 is very low for 7-8 weeks (low end of normal would be close to 8000)  ..  

[buko]

Yes, I know it doesn't look good...  Although it's still hard for me to imagine that it would be ectopic unless we're talking about an ectopic twin? 

I'm sure she will have more answers at her u/s tomorrow.