Ectopic pregnancy – HCG hiccups, some older evidence
When I went to med school we were taught that the B-HCG level doubles every 48 hrs in early pregnancy – and if it wasn’t – you either had an ectopic or a miscarriage until proven otherwise. However, it turns out that this is not the case – just when you thought it was safe to go back to office gynae – along comes some data that completely muddies the waters and makes it all difficult again.
Barnhart et al in 2004 showed the HCG was slower to rise in many women with normal viable intrauterine pregnancies – the 99% confidence for slowest rise (going on to normal pregnancy) was only 53% at 48 hours [eg. from 1000 iu to 1530 2 days later] – tthis is precisely what I thought an ectopic looked like! So I think you need to be careful when interpreting these numbers.
This study out of Oregon in 1990 [Rob Orman was at the peak of his grunge career?] followed a small group of women with high risk pregancies – and 2/3 of the women with ectopics actually had a normal “doubling”.
Kadar et al in 1994 looked at women’s uteri for an intrauterine sac based on both HCG and ‘dates’ and found that ‘dates’ are much better predictors of gestation that HCG. So if you have an idea of LMP or when the HCG first went up – you are better off than using a single HCG.
So that is the bad news – the HCG can really lead you down the garden path if you are not careful. So do NOT rely on a single HCG, be careful of interpreting 48 hour “doubling” HCG levels and if you know the dates- this is actually useful!
The good news – we ED types are actually pretty good when it comes to finding normal IUPs. There was a meta-analysis in 2010 by Stein et al which showed US in ED docs hands was up in the high 90s for sensitivity and specificity for detecting IUP or its absence.
Caveat: you have to practice and get good at interpreting what you see. For a great guide and resources check out Ultrasound Village – their cheat sheets are cool – I use them all the time in my practice.
On the topic of early pregnancy (but not ectopics) – there’s been some recent papers about the criteria for early pregnancy failure suggesting we should be more conservative (although the absolute numbers are small for many of the groups). Various O&G colleges and Ultrasound groups are adjusting their criteria (and we’ll be updating the Ultrasound Village ones as well) – see the press release from ASUM for more details
thats a useful update.
love your website , ultrasound village
Got this comment from Dr Jenna Lineham:
Just wanted to share some information from the ISUOG conference this year.
The stuff on HCG (that the levels have been seen to rise but only 55% over 2 days in viable pregnancy) was what was also being talked about at the ISUOG conference this year. I wanted to also mention that they also discussed cases showing that the BHCG cutoffs where you should expect to see a gestational sac are much too low in most guidelines. One case (the most extreme example) was presented with a BHCG of 22 000, no gestational sac seen. A few days later (could have been 1 or 2 days- can’t remember) two gestational sacs were seen- i.e twins. Final outcome was singleton baby (although can’t remember if this was @ 12 weeks with a heartbeat, or a live birth). In the discussion was many cases where people in the states were given methotrexate after a certain HCG was reached and the uterus was empty (think cut off in many guidelines is generally around 4000-5000) on the grounds that an ectopic was assumed. The conclusion was that it is much safer to follow stable patients with positive HCG and no gestational sac identified and re ultrasound than to intervene with either D&C assuming miscarriage or methotrexate. Similar discussion revolved around fetuses without heartbeat that had failed to grow.. cases were presented where 10 days of no growth was recorded but resulted in a viable pregnancy at 12 weeks. (once again the extreme case, but highlighting that its better to follow stable patients than intervene with D&C as missed miscarriage is not sure).
Adrian- research around your sac diameter and embryo length cut-off was also discussed, – also from London (probably similar research/authors to what is influencing ASUM guideline changes.)