Risk for recurrence of PE & outcome of subsequent pregnancy

[caryn]

Subsequent pregnancies in the PET group were characterized by a higher rate of preterm delivery at less than 37 and 34 weeks (15.2% vs. 5.7%, P<0.001 and 3.8% vs. 0.8%, P<0.001, respectively), placental abruption (1.7% vs. 0.2%, P=0.004), IUGR (2.8% vs. 0.9%, P=0.016), and PET (5.9% vs. 0.8%, P<0.001). Risk factors for PET and adverse outcome in the subsequent pregnancy included: PET complicated by placental abruption in the index pregnancy (OR=10.8, 95%-CI=1.8-34.6), PET requiring delivery prior to 34 weeks in the index pregnancy (OR=6.5, 95%-CI=1.6-22.5), chronic hypertension (OR=5.3, 95%-CI=1.9-12.7), and maternal age>35 (OR=4.3, 95%-CI=1.2-20.5).

http://www.ncbi.nlm.nih.gov/pubmed/22524456

Okay, a lot of numbers. The authors abbreviate preeclampsia as PET (which stands for pre-eclamptic toxemia) - I usually see this done when they are including pulmonary embolism as a potential outcome and are abbreviating it as PE.

It is hard to make columns in this format - I will try to make a graphic and share it later, but for now the first line of numbers is your odds in a second pregnancy if you have a history of preeclamptic pregnancy, and the second is your odds if you do not have that history. So us, compared to normotensive pregnancies.

Condition | our odds | normotensive odds
__________________________________
delivery before 37 weeks | 15.2% | 5.7%
delivery before 34 weeks | 3.8% |0.8%
abruption | 1.7% | 0.2%
IUGR | 2.8% | .9%
preeclampsia | 5.9% | .8%

Obviously, they didn't break out preterm preeclamptics in this data, because that 5.9% risk of recurrence is way lower than it is if you had a baby before 32 weeks. This includes people who hit 140/90 twice and had proteinuria at 39 weeks, got induced, and didn't really realize that they'd had preeclampsia.

Then they give your odds that things will go kablooey, relative to normal odds, for a couple of combinations of issues. If you had preeclampsia and an abruption last time, your chances of preeclampsia and something going wrong this time are 10.2 times higher than normal. Technically, I think they call that "a lot higher." If you had preeclampsia and needed to be delivered before 34 weeks, chances things go wrong are 6.5x higher. If you are a chronic, 5.3x. If you are over 35, 4.3x.

In other words, if you had preterm preeclampsia and you're a chronic over 35 *raises hand* stuff goes kablooey with awesome regularity.

I'll go muck about in Photoshop in a bit.

[eleni]

Hey Caryn - thanks for posting. this is probably the #1 question we get, right? So how important is it that we know who the population is that was studied? Even though the general risk of PE is about the same around the world, there are some differences and I would think that the general health of the population studied might impact/create subtle differences. It is nice to see a fairly high N in this study.

[caryn]

That's one reason I grabbed this and called attention to it - nice high N, nice long time period, good journal - this is an evaluation of subsequent pregnancies in the set of all women with first preeclamptic pregnancies between 1996 and 2008 in the population used, which is a data set from a hospital in Israel.

[caryn]

I want to add - these are increases in your baseline risk. Baseline risk of preeclampsia is around 5% - it occurs in 5 out of 100 pregnancies.

So. If you are at 10.2 times the risk - that is 10.2 times 5. So around 50% of women who fall into the population that's told they're at 10.2x the risk of preeclampsia will have preeclamptic pregnancies. Onset can be much later and milder in subsequent pregnancies, on average, but of course there is no guarantee that this will happen.

That means that for the group of women who are told "hey, you're at really high risk because you had preeclampsia and an abruption last time", roughly half will develop preeclampsia again, and roughly half will not.

The hard thing about all of these numbers is that they are just for a population - not for an individual in that population. A consult with an MFM is the way to get more information about your individual risks.

[LauraBeck12]

So if i am 28 years old and had to have my son at 29 weeks which resulted in his death because of severe pre-e and my placenta was starting to abrupt and he had IUGR and i was hospitalized for 13 days with very high blood pressure (over 140/90 the whole time) and proteinuria... my chances of getting pre-e again are like 100% because i multiply all those chances together?

[caryn]

Oddly, no - because they don't add like that. All of the sets of odds above have "preeclampsia" as a risk factor so you'd be double-counting risk from preterm preeclampsia if you added them.

IUGR plus abruption plus preterm preeclampsia is more risky than just (just!) IUGR and preterm preeclampsia - although they didn't look at the group of women with that set of conditions, because the numbers were still too small to draw any conclusions, so I'm speaking on the basis of what I hear from docs at conferences - but not 100% risky. Nothing about this disease is ever that straightforward.

My guess - just a guess based on what we see here, totally not to be taken seriously and you should ask a doc - is that that would put you at more like ~60% odds, with onset likely later and a slower progression. It's chronics with a history of preterm PE, and a couple of other underlying conditions like lupus, that are looking at odds closer to 100%. And even then posters surprise me regularly with straightforward uncomplicated third pregnancies, or what have you.

[LauraBeck12]

Thank you for breaking that down for me Caryn!
I am grateful for how much knowledge you share with us!

[caryn]

You know, since in this population normotensive risk of preeclampsia was .8%, I wonder if they multiplied by that instead of by the 5% number that I'm in the habit of using? I will have to crunch some numbers...