Objective
The objective of the study was to determine whether eclampsia has a different circulating profile of angiogenic (placental growth factor [PlGF]) and antiangiogenic factors (soluble vascular endothelial growth factor receptor-1 [sVEGFR-1] and soluble endoglin [sEng]) from severe preeclampsia.
Study Design
This cross-sectional study included pregnant women in the following groups: (1) normal pregnancy (n = 40); (2) severe preeclampsia (n = 40); and (3) eclampsia (n = 20). Maternal serum PlGF, sVEGFR-1, and sEng concentrations were determined using an enzyme-linked immunosorbent assay.
Results
The study results included the following: (1) the median concentration of sVEGFR-1 and sEng was higher and of PlGF was lower in severe preeclampsia or eclampsia than in normal pregnancy ( P < .001 for all); and (2) the median concentrations of these 3 analytes did not differ significantly between patients with severe preeclampsia and those with eclampsia.
Conclusion
Eclampsia is associated with higher maternal circulating concentrations of sVEGFR-1 and sEng and lower concentrations of PlGF than normal pregnancy but with similar concentrations to severe preeclampsia. These findings suggest that eclampsia shares a common pathogenic pathway as severe preeclampsia.
Preeclampsia, one of the great obstetrical syndromes, complicates about 2-7% of pregnancies and is a major contributor to maternal and neonatal morbidity and mortality worldwide. In recent years, an imbalance between circulating angiogenic and antiangiogenic factors has emerged as a potential key pathway in the pathophysiology of preeclampsia. Specifically, patients with preeclampsia have a higher circulating concentration of antiangiogenic factors (ie, soluble vascular endothelial growth factor receptor-1 [sVEGFR-1], also called soluble fms-like tyrosine kinase 1 [sFlt1]) and soluble endoglin (sEng)] and a lower maternal circulating concentration of free angiogenic factors (ie, vascular endothelial growth factor [VEGF] and placental growth factor [PlGF]) than patients with a normal pregnancy. These findings have been demonstrated both at the time of the clinical diagnosis of preeclampsia and also prior to the clinical manifestation of the disease.
In addition, the degree of the angiogenic/antiangiogenic imbalance in preeclampsia has been associated with disease severity. Indeed, Venkatesha et al reported that serum sEng concentrations were 3-, 5- and 10-fold higher in individuals with mild preeclampsia, severe preeclampsia, and HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome, respectively, compared with gestational age-matched controls. Therefore, sEng has been suggested to be a marker for severity of disease.
Eclampsia, defined as the occurrence of new-onset grand mal seizures or unexplained coma in a woman with preeclampsia, is a serious and life-threatening complication of pregnancy with an incidence of about 1 in 2000 pregnancies. In approximately two-thirds of cases, the onset of seizures is during pregnancy (antepartum or intrapartum); however, eclampsia can occur in the postpartum period in about one third of cases (range, 11–44%). One of the signs characterizing women as having severe preeclampsia is the eclamptic seizures. However, the classical diagnostic signs of preeclampsia (ie, hypertension and proteinuria) may not precede the eclamptic seizures in more than one third of the cases, and hypertension may be absent in about 20% of cases. Katz et al analyzed a series of 53 cases of eclampsia and found that seizures were the first signs of preeclampsia in 60% of cases. The authors concluded that eclampsia seems not to be a progression from severe preeclampsia.
The underlying pathophysiological process predisposing pregnant women to eclamptic seizures is not clear. Several mechanisms of disease have been implicated in the pathogenesis of eclampsia including hypertensive encephalopathy, cerebral edema, infarction or hemorrhage, endothelial dysfunction, and others. To our knowledge, there are no data regarding the concentrations of angiogenic/antiangiogenic factors in serum from patients with eclampsia and whether the concentrations of angiogenic and antiangiogenic factors in these patients differ from those of patients with severe preeclampsia. Thus, the aim of this study was to compare the profile of circulating angiogenic (PlGF) and antiangiogenic (sVEGFR-1 and sEng) factors in patients with eclampsia and those with severe preeclampsia.
Patients and Methods
Study design
A cross-sectional study was conducted by searching our clinical database and bank of biological samples and included 100 pregnant women in the following groups: (1) normal pregnancy (n = 40); (2) severe preeclampsia (n = 40); and (3) eclampsia (n = 20). Women with multiple pregnancies and fetuses with chromosomal and /or congenital anomalies as well as women with HELLP syndrome or in which eclampsia occurred after the delivery of the placenta were excluded.
All participants provided written informed consent prior to the collection of blood samples. The collection of blood and its utilization for research purposes were approved by the Institutional Review Boards of Wayne State University. Many of these samples have been previously used to study the biology of inflammation, hemostasis, angiogenesis regulation, and growth factor concentrations in normal pregnant women and those with pregnancy complications.
Clinical definitions
Women with a normal pregnancy were defined as those without medical, obstetrical, or surgical complications at the time of the study and who subsequently delivered an appropriate-for-gestational-age infant at term (≥37 weeks of gestation) without neonatal complications. Preeclampsia was defined as the onset of hypertension (systolic blood pressure of ≥140 mm Hg and/or diastolic blood pressure of ≥90 mm Hg on at least 2 occasions, 4 hours to 1 week apart) after 20 weeks of gestation with proteinuria (≥300 mg in a 24 hour urine collection or at least 1 dipstick measurement of more than ≥2).
Severe preeclampsia was diagnosed according to the criteria proposed by the American College of Obstetricians and Gynecologists committee as systolic blood pressure of 160 mm Hg or greater and/or a diastolic blood pressure of 110 mm Hg or greater and/or proteinuria greater than 5 grams in a 24 hour collection or +3 or greater protein on dipstick or in the presence of multiorgan involvement.
HELLP syndrome was defined as hemolysis (serum lactate dehydrogenase greater than 600 IU/L; bilirubin greater than 1.2 mg/dL; presence of schistocytes in peripheral blood), elevated liver enzymes (serum aminotransferase and/or aspartate aminotransferase >70 IU/L); and thrombocytopenia (platelet count <100,000/mm 3 ).
Eclampsia was defined as the occurrence of convulsions in pregnant women who had preexisting gestational hypertension or preeclampsia or as new-onset convulsions in women without a previously known hypertensive or seizure disorder but in whom hypertension (systolic blood pressure of ≥140 mm Hg and/or diastolic blood pressure of ≥90 mm Hg) was part of the clinical presentation.
Blood sample collection and determination of PlGF, sVEGFR-1, and sEng in maternal serum
Maternal blood samples were obtained from normal pregnant women either during an antenatal clinic visit or before a scheduled cesarean section and from women with preeclampsia or eclampsia at the time of diagnosis. Samples of peripheral blood were obtained by venipuncture, centrifuged at 1300 × g for 10 min at 4°C, and stored at -70°C until assayed.
Concentrations of PlGF, sVEGFR-1, and sEng in maternal serum were determined using specific and sensitive immunoassays (R&D Systems, Minneapolis, MN). All 3 immunoassays utilized the quantitative sandwich enzyme immunoassay technique.
Immunoassays were carried out according to the manufacturer’s recommendations. The calculated interassay coefficients of variation (CV) for PlGF, sVEGFR-1, and sEng immunoassays in our laboratory were 5.7%, 6.2%, and 3.8%. Calculated intraassay CVs for PlGF, sVEGFR-1, and sEng were 4.4%, 2.2%, and 2.8%. The calculated detection limit (sensitivity) for PlGF, sVEGFR-1, and sEng assays were 9.2 pg/mL, 16.8 pg/mL, and 0.11 ng/mL, respectively.
Statistical analysis
The Shapiro-Wilk test was used to test for normal distribution of the data. For comparisons among and between groups, ANOVA with posthoc corrections for multiple comparisons (Bonferroni) was used for normally distributed continuous variables and Kruskal-Wallis test with posthoc Mann-Whitney U test was used for continuous variables that were not normally distributed (eg, maternal serum concentrations of PlGF, sVEGFR-1, and sEng). Comparison of proportions was performed using the Fisher’s exact test. Correlations between continuous variables were examined using the Spearman’s rank correlation test. A multivariable logistic regression analysis was applied to determine the association between serum concentrations of PlGF, sVEGFR-1, and sEng (and their ratios) and eclampsia and adjusting for maternal age, gestational age at blood drawn, and sample storage time among patients with severe preeclampsia and those with eclampsia (pooled together). A P value < .05 was considered statistically significant. The analysis was performed with SPSS, version 12 (SPSS Inc, Chicago, IL).
Results
Demographic and clinical characteristics
The demographic and clinical characteristics of the study population are shown in Table 1 . There were no significant differences among the study groups in the medians of any of the demographic characteristics as well as in the median gestational age at blood drawn. As expected, the patients with severe preeclampsia or eclampsia had significantly higher medians of maximal systolic and diastolic blood pressure and lower medians of gestational age at delivery and neonatal birthweight than women with a normal pregnancy. None of these variables differed significantly between patients with severe preeclampsia and those with eclampsia.
