Predicting Risk of Chronic Hypertension in Women with Preeclampsia Based on Placenta Histology. A Prospective Cohort Study in Cuba.

Background: Chronic hypertension is one of the major sequelae of preeclampsia with associated long term morbidity and mortality among previously normotensive women diagnosed with preeclampsia. We identied the predictors of developing this complication in women with preeclampsia admitted at the Carlos Manuel de Cèspedes Teaching Hospital in Cuba based on histological assessment of their placenta so as to guide the health care providers in early identication of the patients at risk for timely intervention against this vicious condition. Methods: A three-year prospective cohort study was conducted between March 2017 and March 2020. A cohort of 178 women diagnosed with preeclampsia was recruited and followed up at 12 weeks postpartum for chronic hypertension. Histological studies were done on their placenta following delivery and the respective result forms used to collect the data. Cox’s hazards regression model was applied to estimate the risk using STATA version 14.2. Results: Chorioamnionitis (HR=1.697, 95%CI: 1.443-3.416, p=0.038), villositary infarcts (HR=1.657, 95%CI: 1.264-2.848, p=0.048), intervillositary thrombus (HR=1.529, 95%CI: 1.231-3.197, p=0.020), and endarteritis (HR=1.242, 95%CI: 1.115-1.804, p=0.025) placental lesions were predictive of chronic hypertension at 12 weeks postpartum. Conclusion: Placental histology in women with preeclampsia is key towards improving the ability to diagnose and monitor those likely to develop chronic hypertension before its onset for timely intervention.


Background
Chronic hypertension and preeclampsia remain one of the most intriguing hypertensive disease conditions among obstetricians all over the world with associated high maternal and neonatal morbidity and mortality (1). The two are part of the four classi cation criteria for the different forms of hypertensive disorders of pregnancy; the other two being gestational hypertension and preeclampsia superimposed on chronic hypertension (2)(3)(4). Chronic hypertension is de ned as one (systolic blood pressure more than or equal to 140 mmHg and diastolic blood pressure more than or equal to 90 mmHg taken four to six hours apart) that is diagnosed before pregnancy or before 20 weeks of gestation; or one that is rst diagnosed after 20 weeks' gestation and persists for greater than 12 weeks postpartum (5)(6) (7). In Cuba, preeclampsia is among the leading causes of maternal deaths and there has been an apparent rise in the proportion of maternal mortality related to hypertensive disorders of pregnancy since 2009 even though numbers are small (for example, a rate of 3.2 per 100,000 live births was reported in 2012) (8). Generally, a high future risk of up to 14.8% of developing chronic hypertension in women with preeclampsia (versus 5.6% in those without preeclampsia) has been reported (9). This persistent (chronic) hypertension has been noted to be a major threat to the quality of life of the women (10) with greatly increased risk of adverse cardiovascular events such as stroke, renal failure and coronary heart diseases (11)(12)(7)(13) The predictive factors for chronic hypertension following preeclampsia pregnancies however remain not very clear; not only in Cuba but even to most of the other parts of the world. For quite a long time, the placenta has attracted a lot of attention among many scholars world over with regard to its role in the aetiopathology of preeclampsia. Most theories relate to a failed transformation of the spiral arteries during placentation with subsequent release of certain factors which lead to endothelial dysfunction, generalized vasospasms and ultimately impaired multiple organ function (16) (17) (18) (19). The altered organ function can lead to persistence of hypertension depending on the severity of the endothelial dysfunction even after delivery of the placenta (13). Early interventions tailored at controlling the high blood pressure during the postpartum period may result in reduction in associated morbidity and mortality resulting from this chronic hypertension (20) (21). The aim of the current study was to identify the histological predictors of this persistent hypertension based on the patient's placenta following delivery so as to guide in easy and timely identi cation of those at risk for early initiation of relevant interventions so as to minimize associated complications.

Methods
This was a prospective cohort study conducted collaboratively between Granma University of Medical Sciences in Cuba and Kampala International University in Uganda over a period of three years in the months of March 2017 to March 2020. The study was conducted in the hypertension unit of Obstetrics and Gynaecology department of Carlos Manuel de Cèspedes Teaching Hospital located in Bayamo city, Granma Province, Southeastern Cuba. This is a public tertiary teaching hospital for the University of Medical Science of Granma with a bed capacity of 879. The obstetric unit where the study was done has a bed capacity of 234 and conducts about 5000 deliveries per year according to the hospital records of 2019. A total of 178 pregnant women above 24 weeks of gestation admitted in the hypertension unit with a diagnosis of preeclampsia that consented to participate in the study were enrolled. Consecutive enrolment of all the pregnant women who met the inclusion criteria for the study was done until the required sample size was realised. Diagnosis of preeclampsia was made following the American College of Obstetricians and Gynaecologists' protocol 2016 (12). Preeclampsia was de ned as the presence of hypertension of 140/90 mmHg or more repeated four hours apart with proteinuria of + 1 or more in a previously normotensive patient above 20 weeks of gestation (22)(23). Only women above 24 weeks of gestation were however included in the study since we also targeted doppler ultrasound scan results at 24 weeks of gestation. Women with preeclampsia superimposed on chronic hypertension were excluded from the study since they were already chronically hypertensive. Women with known history of kidney disease were also excluded from the study since serum creatinine was one of our study variables. This is usually deranged in patients with kidney disease. These three variables were particularly being considered in a different investigation. Sample size was 178, estimated using Daniel's formula (24).
Voluntary recruitment of all the study participants was done. Informed written consent from the participants was obtained after fully explaining the details of the study in Spanish, the national language for Cuba. An informed consent document in Spanish language approved by the research ethics committee of Carlos Manuel de Cèspedes Teaching Hospital was signed by every participant, the investigator and a witness. Participants were not forced to enroll if they did not want to. The participant was free to withdraw from the study at any time she wished, without coercion or compromise of care that she was entitled to. Blood pressure measurements were done using a manual mercury sphygmomanometer using the right hand at the level of the heart with the patient in sitting position. All the enrolled participants were managed according to the hospital protocol which includes antihypertensive drugs, administration of magnesium sulfate for those with severe preeclampsia and subsequently delivery. A histopathologist was noti ed of any impending delivery. On delivery, the placenta was received on a bowl and then assessed for any gross abnormalities. Samples were then collected in 10% formaldehyde solution and transported to the histopathology laboratory within ten minutes for further analysis. Here, the tissues were stained using Haematoxylin and Eosin (H&E) and analyzed for any abnormalities such as intervillository thrombus, villository infarcts, tennar parker changes, placental hypermaturity, chorioamnionitis, meconium, decidual necrosis and endarteritis. 10% of our samples were sent to an independent histopathologic laboratory in Bayamo province for analysis for purposes of quality assurance. To avoid bias, every 10th sample was submitted for this cause. Laboratory forms were used to collect the data. Participants were followed up at twelve weeks post-delivery and their blood pressure measurements re-taken as already explained above so as to ascertain their blood pressure status. Those whose blood pressure were still above or equal to 140 mmHg systolic and 90 mmHg diastolic were considered to have chronic hypertension. Individuals with a systolic blood pressure lower than 140 mmHg and diastolic blood pressure lower than 90 mmHg were de ned as normotensive. All the collected data were entered into Microsoft excel version 2010 and then imported into STATA version 14.2 for analysis. Both univariate and Cox's multivariate model analyses were carried out to estimate the risk.
The variables in the nal multivariate model were signi cant when p < 0.05. The measure of association was reported as hazard ratios with corresponding 95% con dence interval and p-value.

Results
A total of 178 women with preeclampsia were enrolled over the period of three years. Nine patients were however excluded from the study due to superimposed preeclampsia on chronic hypertension. Four women had history of isolated renal disease (that is, had history of only renal disease without chronic hypertension) and were also excluded while three patients failed to attend the postnatal follow-up at twelve weeks. Therefore, only 162 patients were successfully studied and data analyzed. Out of a cohort of 162 participants, 45(27.8%) had chronic hypertension at twelve weeks postpartum. The most common pathological ndings were endarteritis 93(57.4%), followed by villository infarcts 42(25.9%) and chorioamnionitis 25(15.4%). We noted very few cases of decidual artery disease 3(1.9%) and this was the lowest histopathological nding found. These are shown in Table 1.
Based on these ndings therefore, and as it has been suggested by Garovic and August (27), it is possible that the preeclampsia induced long-term irreversible vascular changes arising from these placental lesions may be responsible for the overall increased risk for chronic hypertension and other related longterm cardiovascular sequel of preeclampsia. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
We bear no any competing interests to declare.

Funding
No funding was obtained for this study.
Authors' contributions SB was involved in conceptualization and design of the study, analysis, manuscript writing, and coordination of the study team. YF participated in conceptualization, design, data collection, and analysis of the study. DN and AA made substantial contribution during data collection and analysis. YC contributed towards study design, data and sample collection, and analysis of samples in the histopathology laboratory. RS made substantial contribution towards study design, literature search and general revision of the manuscript. All the authors had su cient time to read and approve the nal manuscript.