What is Eclampsia Anyway?

Eclampsia is the onset of seizures in a pregnant woman with pre-eclampsia.  It is a Very Bad Thing.  Complications of eclampsia can kill the mother (about a 1% chance).

Ok, so what’s pre-eclampsia? A disorder, usually in the third trimester, that involves high blood pressure, protein in the urine, and other problems such as liver or kidney dysfunction.

What causes it? It’s mostly unknown.

The hypothesis [1] seems to be something like “systemic inflammation” or an immune response of the mother to the placenta; this would explain why obesity, insulin resistance, maternal infections, and miscarriages are associated with increased risk of pre-eclampsia.  Pro-inflammatory cytokines such as TNF (chemicals produced by the body’s innate immune response) can constrict blood vessels and cause microvascular protein leakage, which is a potential cause of the high blood pressure and proteinuria.  High blood pressure, if untreated, causes edema (swelling) in various tissues, including the brain, and that pressure can cause seizures.[1]

Even typical pregnancy is characterized by a strong inflammatory response, and some believe that pre-eclampsia is simply an extreme case of what happens in all pregnant women.[1]

Pre-eclampsia occurs in 2-7% of pregnant women.  Usually, the high blood pressure is treated with beta blockers, and sometimes magnesium sulfate is given to prevent seizures.

What are the risk factors for pre-eclampsia?

 

PIGF. Placental growth factor helps blood vessels develop around the placenta; women who develop pre-eclampsia have lower levels of it in the first trimester. The bottom tertile of PIGF levels have 28x the risk of pre-eclampsia of the top tertile.[5] A larger study found that women in the bottom quartile of PIGF levels had an odds ratio of 19.6 compared to the top quartile.[6]  Failure to grow new blood vessels seems to result in failure of the placenta and endometrium to successfully mesh, which causes hypertension since deoxygenated blood can flow out of the placenta but oxygenated blood cannot easily flow in.[7]

Antiphospholipid Antibodies. The presence of these is associated with a relative risk of 9.72 of pre-eclampsia.[2]  Antiphospholipid antibodies are caused by an autoimmune problem where the body attacks proteins that attach to cell membranes, causing an increased rate of blood clotting and miscarriage.

Diabetes. Pre-existing (not gestational) diabetes is associated with a 3.56x risk of pre-eclampsia.[2]

Twins. The relative risk of pre-eclampsia in twin pregnancies is 2.93x the risk for singletons.[3]

Family history. The risk of pre-eclampsia for those with a family history of pre-eclampsia is 2.90x the risk for those without.[3]

Smoking. The risk of pre-eclampsia in smokers is 2.67x the risk in nonsmokers.[4]

Overweight. The relative risk of pre-eclampsia for those with prepregnancy BMI > 25 is 2.47.[3]

High blood pressure. The relative risk of pre-eclampsia for those with systolic BP > 130 at the start of pregnancy is 2.37 compared to those with BP < 130 at the start of pregnancy.[3]

Bottom Line:

As for many of the disorders of pregnancy, being in “general good vascular health” is helpful. (It’s better not to smoke, not to have diabetes or high blood pressure, not to be overweight, etc.)  Predisposition to pre-eclampsia also seems to have a strong genetic component; family history increases risk, as does having previous pregnancies with pre-eclampsia, or previous miscarriages; inherited issues like antiphospholipid antibodies, and potentially other genes, increase risk.  Once you’re pregnant, there doesn’t seem to be that much you can do to prevent pre-eclampsia, though detection and treatment can keep it from progressing to eclampsia or other dangerous problems.

 

References

[1]Sibai, Baha, Gus Dekker, and Michael Kupferminc. “Pre-eclampsia.” The Lancet 365.9461 (2005): 785-799.

[2]Walker, James J. “Pre-eclampsia.” The Lancet 356.9237 (2000): 1260-1265.

[3]Duckitt, Kirsten, and Deborah Harrington. “Risk factors for pre-eclampsia at antenatal booking: systematic review of controlled studies.” Bmj 330.7491 (2005): 565.

[4]Ødegård, Rønnaug A., et al. “Risk factors and clinical manifestations of pre‐eclampsia.” BJOG: An International Journal of Obstetrics & Gynaecology107.11 (2000): 1410-1416.

[5]Thadhani, Ravi, et al. “First trimester placental growth factor and soluble fms-like tyrosine kinase 1 and risk for preeclampsia.” The Journal of Clinical Endocrinology & Metabolism 89.2 (2004): 770-775.

[6]Levine, Richard J., et al. “Soluble endoglin and other circulating antiangiogenic factors in preeclampsia.” New England Journal of Medicine355.10 (2006): 992-1005.

[7]Wang, Alice, Sarosh Rana, and S. Ananth Karumanchi. “Preeclampsia: the role of angiogenic factors in its pathogenesis.” Physiology 24.3 (2009): 147-158.

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