Research ArticleThe relationship between hypertensive disorders in pregnancy and placental maternal and fetal vascular circulation
Introduction
Placental dysfunction has been considered as a potential pathogenic mechanism in the development and progression of hypertensive disorders in pregnancy (HDP). The ischemia as well as hypoxia of placenta prompts an adverse maternal circulatory milieu, leading to excessive production and release of proinflammatory cytokines, defective angiogenic factors, and reactive oxygen species.1, 2, 3, 4, 5 These bioactive factors target blood vessels, resulting in vascular smooth cell hypertrophy and endothelial dysfunction, which eventually lead to vasoconstriction, increased peripheral vascular resistance, and hypertensive disorders.6, 7 HDP include several different, but linked, conditions: chronic hypertension (HTN) (ie, predates the pregnancy or has onset before 20 weeks' gestation), HTN arising de novo in pregnancy from 20 weeks’ gestation (gestational HTN), and gestational HTN accompanied by proteinuria (preeclampsia) and seizures (eclampsia). While all pregnancies complicated by HTN are associated with an increased risk of fetal and maternal adverse outcomes, the three categories of hypertensive disorder during pregnancy impact in a different way maternal and perinatal morbidity and mortality.8, 9, 10 Large clinical studies have demonstrated that preeclampsia is associated with higher rates of maternal as well as perinatal morbidity and mortality, whereas mothers with chronic HTN have increased rates of major neonatal morbidity and fetal death.7 However, no studies have examined the effect of different types of hypertensive disorders on maternal and fetal placental vascular circulation. The present study was designed to examine the impact of chronic HTN, gestational HTN, and preeclampsia in pregnancy, on placental maternal and fetal vascular circulation.
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Methods
The medical records of women who gave birth and underwent a placental histopathologic examination between 2007 and 2013 at the Department of Obstetrics and Gynecology, Edith Wolfson Medical Center, were reviewed. Our department routinely performs placental analyses in all patients with a complicated pregnancy, including maternal diseases during pregnancy (eg, hypertensive disorders and diabetes) and fetal abnormalities (eg, fetal growth restrictions and intrapartum nonreassuring fetal heart
Placental Examination
Placental histology was analyzed according to the criteria of the Society of Pediatric Pathology,11 with the 2016 Amsterdam Placental Workshop Group Consensus Statement modifications.12 Placental pathology examinations were performed using our standard protocol as we previously reported.13, 14 From each placenta, six tissue samples were embedded in paraffin blocks for microscopic assessment. Corresponding with the guidelines of the Society for Pediatric Pathology, we classified the placental
Statistical Analysis
Analysis of data was carried out using SPSS 9.0 statistical analysis software (SPSS Inc, Chicago, IL, 1999). Categorical variables were compared between groups using the chi-square test and presented as frequency (percentage). Distributions of continuous variables were assessed for normality using the Kolmogorov–Smirnov test. Normally distributed continuous variables were described using mean ± standard deviation. Variables with distributions significantly deviating from normal were described
Results
The clinical characteristics of the study groups are presented in Table 1. One hundred and forty pregnant women were divided into four groups according to the type of hypertensive disorder: Group 1 included 25 women with chronic HTN; Group 2 included 28 women with gestational HTN; Group 3 included 34 women with preeclampsia; and Group 4 consisted of 53 women without hypertensive disorder, matched by age, gravidity, parity, and mode of delivery.
Placental findings of the study groups are
Discussion
In the present study, the rate of placental MVM was significantly higher in pregnant women with chronic HTN and preeclampsia: Chronic HTN emerged as a significant predictor of MVM and more than sixfold increased the risk of this outcome, while preeclampsia more than tripled the risk of placental vascular maternal malperfusion. Although increased rate of PMM was observed in women with gestational HTN compared with women without HTN, this difference did not reach statistical significance.
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Conflicts of interest: There are no conflicts of interest. All authors read and approved the final article.