Pre-eclampsia is diagnosed when a pregnant woman develops high blood pressure (two separate readings taken at least 6 hours apart of 140/90 or more) and 300 mg of protein in a 24 hour urine sample (proteinuria). Swelling or edema(especially in the hands and face)was originally considered an important sign for a diagnoses of pre-eclampsia, but in current medical practice only hypertension and proteinuria are necessary for a diagnoses.

Some women develop high blood pressure without the proteinuria, this is called Gestational Hypertension or, Pregnancy Induced Hypertension (PIH). Both Preeclampsia and PIH are very serious conditions and require careful monitoring of mother and baby.

Appearance

Pre-eclampsia is much more common in the first pregnancy (3-5% of births) and usually becomes evident in the third trimester (and virtually always after the 20th week of pregnancy). It is also more common in women who have preexisting hypertension, diabetes,renal disease, and family history of pre-eclampsia. It is also more common in women with a multiple gestation (twins, triplets and more).

Pre-eclampsia may also occur in the immediate post-partum period or up to 6-8 weeks post-partum. This is referred to as "post partum pre-eclampsia".

Causes

Pre-eclampsia is thought to be caused by inflammatory mediators secreted by the placenta and acting on the vascular endothelium. If severe, it progresses to fulminant pre-eclampsia, with headaches and visual disturbances, and further to HELLP syndrome and eclampsia. These are life-threatening conditions for both the developing fetus and the mother.

Pathogenesis

There are many theories on the pathogenesis of preeclampsia, although the exact cause is not known. Most involve abnormal development of the placenta, which leads to a distressed placenta that secretes factors into the maternal blood. These factors damage the maternal blood vessels, leading to high blood pressure and protein in the urine. In normal placenta the decidual spiral arteries are invaded by extravillous trophoblasts which makes the arteies eventually open into trophoblastic cavities called lacunae (though they are initially kept plugged by the trophoblasts). The invading trophoblasts replace some of the smooth muscles and endothelium of these arteries near the implantation site. This is supposed to help the spiral arteries to widen into thin and funnel like near their opening into the lacunae. This establishes a high capacity and low resistance circulation. The maternal blood in the lacunar network bath the chorionic villi lined by syncytiotrophoblast, supplying oxygen and nutrients to, and removing metabolic wastes from, the fetal circulation which is not in direct contact with the maternal blood. In case of preeclampsia the spiral arteries are insufficiently invaded by trophoblasts. They remain narrow and the smooth mucle layer (tunica media) around the arteries become hyperplastic. This leads to insufficient maternal perfusion of the placenta in preeclampsia. One of the factors, released into blood from the placenta, that has been speculated (by Karumanchi et al) to be a mediator of the "toxemia", is a soluble splice variant isoform of the VEGF receptor 1 (sFlt 1).

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Warn patients about heart risks after preeclampsia: preeclampsia is a manifestation of underlying silent disease that will develop later into a clinical
From OB/GYN News, 5/1/05 by Carl Sherman

NEW YORK -- Women who develop preeclampsia should be counseled about the risk in subsequent gestations and strategies to contain these risks, according to Baha M. Sibai, M.D.

In addition, more general implications about health in later life should be discussed with the patient, said Dr. Sibai, who is professor and chairman of obstetrics and gynecology at the University of Cincinnati.

He made his report at an obstetrics symposium sponsored by Columbia University and New York Presbyterian Hospital.

About 20%-30% of women who have had an episode of preeclampsia will develop the disorder in a subsequent pregnancy, which makes this history at least as significant a risk factor for future preeclampsia as chronic hypertension, renal disease, and pregestational diabetes.

The earlier in the first gestation preeclampsia developed, the higher the risk of recurrence in the next: the condition returned in more than half of women who had their first episode before week 27, compared with a 40% recurrence when the index episode was between week 27 and 30, and 20% at week 37 or after.

A severe episode of preeclampsia or eclampsia also is associated with a worse outcome in subsequent pregnancies, with an increased risk of intrauterine growth retardation, perinatal loss, and abruptio placentae. Here, too, the earlier the episode occurred in the first gestation, the greater the risk to the second, Dr. Sibai said.

Preventive measures can contain the risk of preeclampsia and poor outcome in subsequent pregnancies. These include attention to weight, blood pressure, and blood sugar.

"Aggressive control of hypertension before and early in pregnancy can reduce the risk of preeclampsia from 50% to [a range of] 10%-15%," Dr. Sibai commented.

In women with diabetes, good control of blood sugar from early in the pregnancy will markedly reduce the rate of preeclampsia, he said.

In vitro fertilization should involve the transfer of no more than two embryos, as a risk-containment measure.

A number of other strategies have been suggested to reduce the incidence of preeclampsia. Prophylactic aspirin has had particular attention, but a large multicenter trial found no difference in outcome among women at highest risk. A meta-analysis of studies using calcium supplementation likewise found no benefit.

Women who have had preeclampsia should also be counseled about its implications for health problems later in life, such as chronic hypertension, diabetes, and ischemic heart disease.

"Preeclampsia is a manifestation of underlying silent disease that will develop into a clinical condition that develops later; it doesn't cause [later health problems]," he said.

The incidence of chronic hypertension in women who have had a severe episode of preeclampsia, at an average follow-up of 7 years, ranges from 7% when the preeclampsia developed after 37 weeks, to 25% when it had developed before 27 weeks.

The risk of later renal and cardiovascular disease is particularly heightened after an episode of preeclampsia that developed before 30 weeks' gestation, that was severe, or that recurred, according to Dr. Sibai. In fact, he said, preeclampsia during one singleton gestation doubles the risk of ischemic heart disease and raises it nearly threefold when preeclampsia is severe.

Gestational hypertension without proteinuria is associated with a 1.6 relative risk of ischemic heart disease.

"The risk factors for preeclampsia and coronary artery disease overlap considerably," Dr. Sibai observed during the meeting.

BY CARL SHERMAN

Contributing Writer

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