Hypertensive disorders (HD) of pregnancy constitute a perplexing and clinically challenging group of complications of pregnancy and are responsible for a substantial burden of illness. They are a leading cause of maternal and perinatal mortality and morbidity worldwide, but especially in developing countries [1].

Preeclampsia is a multisystem disorder of unknown aetiology characterized by development of hypertension with proteinuria after 20^th week of gestation, in previously normotensive and non proteinuric pregnant women [2] [3].

Preeclampsia when complicated with generalized tonic-clonic convulsions and/or coma is called Eclampsia [4].

Globally HD of pregnancy complicate approximately 5% - 10% of pregnancies [5] [6] [7]. The incidence of preeclampsia and the precursor of eclampsia, vary greatly worldwide. Preeclampsia complicates about 2% - 8% of all pregnancies [7] [8].

WHO estimates the incidence of preeclampsia to be seven times higher in developing countries (2.8% of live births) than in developed countries (0.4%) which is due to poor health seeking behaviours and lack of availability of health care facilities and personnel [9].

Incidence of HD of pregnancy in India is found to be 11,266 out of 111,725 deliveries (10.08%) as observed through the data collected by the National Eclampsia Registry (NER) over 3 years (2011-2013) [10]. Two thousand five hundred fifty-four of those 11,266 patients presented with eclampsia [10]. The FOGSI-ICOG NER has brought forth some revealing trends. Eclampsia prevalence among registry patients is 1.9% [10]. National sample surveys in the past have shown prevalence to be 1% - 5%. This is out of the 11,725 deliveries analyzed from the cases reported by 175 reporting centers. Seventeen percent of preeclampsia patients are actually in the adolescent age group reflecting the very early age at marriage in spite of several awareness programs and legal guidelines [10]. 76.34% of the patients were between 21 and 30 years of age thus rendering a very young population morbid and at risk of mortality. It is also a disease of the first-time pregnant woman as 81% of the patients with preeclampsia are primigravida [10].

Approximately 72,000 pregnant women die every year because of eclampsia and severe preeclampsia worldwide [10]. HD account for 16% of all maternal deaths in developed countries [11]. The risk that a woman in a developing country will die of preeclampsia or eclampsia is about 300 times that of a woman in a developed country [12] [13] [14].

Reliable statistics about women dying due to preeclampsia-eclampsia are difficult to obtain because of the poor quality of vital statistics registration systems and hospital records in many developing countries. In addition, a sizable number of deliveries take place at home, and thus there are no records at all for these births [15] [16] [17] [18]. Therefore, data on women who die from preeclampsia-eclampsia are only available from a limited number of countries. Nevertheless, it is clear that the case fatality rates for preeclampsia-eclampsia vary greatly across countries, with the risk of death from preeclampsia-eclampsia being much higher in developing countries than in developed ones [19]. India is among those countries which have a very high MMR, i.e. 190 per 100,000 live births [20]. Hypertension accounts for 5% of maternal deaths in India [21].

HD is also associated with preterm birth, foetal growth restriction, perinatal death and long-term adult health problems in the offspring. Preeclampsia causes five fold increase in the perinatal mortality, with most of the deaths caused by iatrogenic prematurity [22] [23]. In US, preeclampsia is responsible for 15% of premature births [24].

If the disorder occurs in early pregnancy, 53% of the infants are small for gestational age (SGA) [25]. Further, to be born SGA increases the risk of hypertension, diabetes and coronary heart disease as adults [26].

The risk of delivery of low birth weight (LBW) or growth-restricted babies in mothers with HD differs in different ethnic/racial groups [27] [28].

However, the causes for preeclampsia-eclampsia remain unclear and thus preeclampsia-eclampsia has been called a “Disease of theories” [29]. Almost everyone (from an allergist to zoologist) had proposed a theory and almost anything on the earth (from watermelon season to a specific worm infestation) has been blamed [30] [31]. Although the precise cause is unknown, the pathophysiologic processes underlying this disorder are described in two stages [32]. The first stage is characterized by reduced placental perfusion possibly related to abnormal placentation with impaired trophoblast invasion and inadequate remodeling of the uterine spiral arteries. The second stage refers to the maternal systemic manifestations with inflammatory, metabolic, and thrombotic responses converging to alter vascular function which can result in multi-organ damage [33] [34] [35].

Some risk factors for HD of pregnancy has been identified and these include nulliparity, older maternal age, multiple births, diabetes, chronic hypertension, obesity, previous h/o preeclampsia, family history of preeclampsia, a new partner and/or about 10 years since last pregnancy, renal disease, and the presence of antiphospholipid antibodies [7] [33] [36] - [43]. Studies have reported a 7% - 20% chance of recurrence of preeclampsia in a subsequent pregnancy [40] [44] [45].

Some other risk factors are still being investigated. Geographic, social, economic and racial differences are thought to be responsible for incidence rates up to 3 times higher in some populations [46].

Some studies have investigated racial and ethnic factors and identified some differences in severe preeclampsia and eclampsia in different population groups [18] [47] [48] [49] [50]. Among the major ethnic groups considered, East Asian women had the lowest risk of preeclampsia and Mexican women had the highest risk [47].

Caughey reported that the rates of preeclampsia were higher among African American women and lower among Latina and Asian women with all results being statistically significant as compared with white women [48]. Marcelo reported that immigrant women from the Caribbean, Sub-Saharan Africa and Hispanic America were at the highest risk of serious preeclampsia relative to immigrant women from industrialized nations [49]. In a study by Abubakar, among three tribal groups, the preeclamptic Fulani women are more likely to progress to eclampsia than the Hausa and Kanuri [18]. Black women were more likely to be diagnosed with preeclampsia than were White women [50]. The risk of preeclampsia-eclampsia may differ by maternal ethnicity [48] as also the course, severity and prognosis [18] [51] [52]. Such differences in severe preeclampsia and eclampsia in different ethnic population groups may also exist in India. But studies focussing on such aspects of preeclampsia and eclampsia in different population groups in India are scarce in literature. Ethnicity reflects many potential influences on health, including socioeconomic status, lifestyle (e.g. diet and physical activity), medical care utilization, and genetic background associated with geographic origin. Examining the relation of ethnicity with preeclampsia-eclampsia may provide important information that may highlight ethnic subgroups which need to be monitored more actively and could help guide screening and treatment, particularly in light of ethnic diversity of pregnancies [47].

The objectives of this study were to note whether any differences existed among tribal and nontribal women with severe preeclampsia and eclampsia in the Jangalmahal area of West Bengal due to different ethnicity in the following parameters:

· Incidence.

· Clinical and demographic picture.

· Severity and course of disease.

· Response to treatment and complications.

· Delivery outcome including foetal and maternal outcomes.

Specific Objective:

To identify the ethnic/racial group at higher risk of severe preeclampsia and eclampsia among tribal and nontribal women.

In the presented study, there were 65 mothers in Tribal (T) group and 135 mothers in Nontribal (NT) group. Of them 133 mothers had severe preeclampsia and 67 mothers had eclampsia. Total number of deliveries conducted in this hospital was 3768 during the study period. Out of this tribal women were 576 and nontribal women were 3192. Thus, during the study period the overall incidence of severe preeclampsia and eclampsia in our institution were 3.53% and 1.78% respectively. The incidence of severe preeclampsia and eclampsia in tribal women were 7.29% and 3.99% respectively, and in nontribal women were 2.85% and 1.38% respectively. The incidence was found to be significantly (p < 0.001) higher in T group than NT group. Other studies which have examined the association of maternal ethnicity and severe preeclampsia and eclampsia also found some ethnic groups at higher risk than other ethnic or racial groups. Myles Wolf et al. found Hispanic ethnicity to be independently associated with increased risk for preeclampsia and decreased risk for gestational hypertension [55] [56] [57] [58] [59]. Bryant AS et al. found Black women with hypertension in pregnancy in the absence of chronic hypertension more likely to be diagnosed with preeclampsia than were White women [50].

Advanced maternal age has been found to be an independent risk factor for preeclampsia, while in this study most of the mothers of both T and NT group were under 25 years of age, which is probably because we were dealing with women from rural area, where early marriage is more common. The incidence of severe preeclampsia and eclampsia was significantly (p < 0.05) higher in tribal women of 20 yrs and below than NT group, whereas in 21 to 25 yrs of age group nontribal women were found to be more affected than tribal women. Myles Wolf et al. found that Hispanic women were younger than non-Hispanic and Caucasian groups [59] [60] [61] [62]. Goodwin AA et al. reported that Caucasian women were older (27 vs. 24 yrs) than African American women [51].

In our study, severe preeclampsia and eclampsia were more common in nulliparous and primiparous women of both groups but the incidence was significantly (p < 0.05) higher in nulliparous tribal women (86.15%) than nontribals (80%), whereas primiparous mothers were significantly more common in nontribal group (16.30%) than tribal group (10.77%). Goodwin AA et al. found Caucasian women more likely nulliparous than African American and Hispanic women [51]. Depending on ethnicity, the incidence of preeclampsia ranges from 3% to 7% in healthy nulliparas [36]. Gaurav Ghosh et al. reported that nulliparous Hispanic women and Asian/Pacific Islanders had an overall decreased risk compared to non-Hispanic whites [52]. A. K. Rao et al. found that among primiparous women, there is a disparity among ethnic groups as the risk in African American women is twice that of Caucasian women, and the risk is also very high in women of Indian and Pakistani origin [63] - [73].

In the presented study, T group demonstrated more severe hypertension than NT group. Goodwin AA et al. found that African Americans had more severe hypertension where as Hispanic women had less severe hypertension [51].

In our study, Mothers in both groups responded well to treatment but control of blood pressure to the desired level required ≥1 hour of anti-hypertensive therapy (and thus larger doses) in significantly (<0.01) more number of tribal mothers (43.14%) than nontribal mothers (32.65%). Tribal mothers were found to be less responsive to treatment than nontribal mothers, whereas nontribal mothers responded earlier and to a smaller dose of anti-hypertensive drug than tribal mothers, and thus needed a smaller dose of anti-hypertensive drug than tribal mothers. This finding is in agreement with what Goodwin AA et al. found among African American women as they needed more antihypertensive treatment intrapartum, postpartum and at discharge (p < 0.03) than Hispanic women [51].

No significant (p > 0.05) difference in recurrence of convulsion after anticonvulsant treatment was found between the two groups. Goodwin AA et al. found no difference in severe proteinuria among Caucasian, African American and Hispanic women [51] whereas in our study, proteinuria was significantly more common in T group, but severe proteinuria (≥3+), though uncommon in both groups, was more common in nontribals.

T group presented with poorer GCS score on admission than NT group. Nontribal women experienced more number of convulsions than T group.

Regarding the obstetrical condition on admission, most of the tribal and nontribal women had gone into labour, but it was found significantly more commonly in T group, while antepartum (not in labour) mothers were significantly (p < 0.05) more common in nontribal group than tribal group (36.30% Vs 27.69%). In our study, tribal women found in stage I of labour were 56.9% and in stage II were 10.77%, which was significantly (p < 0.05) higher than 51.85% and 7.4% respectively of nontribal women.

In our study, 30.65% of tribal women were delivered vaginally and 6.45% were delivered by assisted vaginal delivery (forceps delivery), which were significantly higher than nontribal women, 20.93% and 3.10% respectively. 75.97% of nontribal women were delivered by lower segment caesarean section (LSCS) than 62.9% tribal women. Myles Wolf et al. found that Hispanic women were less likely to deliver by Caesarean section than non-Hispanic Caucasian groups.

There were no cases of undelivered in our study. There was no significant difference found between T and NT group regarding modes of delivery in postpartum mothers.

In our study, regarding the maternal outcome, maternal mortality was significantly more common (p < 0.05) in the tribal group (10.77%) than the nontribal group (5.92%). Maternal mortality was reported to be high among various tribal groups due to hypertensive disorders of pregnancy [74]. Black women with preeclampsia-eclampsia are more likely to die from these conditions than White women [75] [76] [77] [78].

The T group, in our study, found to be at higher risk of getting complicated with cerebrovascular accidents when they develop severe preeclampsia or eclampsia than NT group, whereas pulmonary embolism was found to be more common in nontribal women. Aparna Khan et al. found cerebral haemorrhage (40%) as the most common cause of death in their study. In Africa, 45.5% of hypertensive maternal death was due to cerebral complications. Goodwin AA et al. found that Caucasian women have more frequent HELLP syndrome [51]. Tribal mothers needed admission to ICU significantly (p < 0.01) more commonly (12.31%) than nontribal mothers (5.92%). There was no significant difference found between T and NT group for duration of hospital stay.

Regarding the foetal outcome in T and NT group, in our study, the incidence of live births and stillbirths were similar in both groups. The new born babies of nontribal mothers suffered significantly more commonly from birth asphyxia than new borns of T group (17% vs 5%). In two studies by Goodwin AA et al. [51] and Myles Wolf et al. [59], no difference in foetal death rates was found among different ethnic groups. There was one neonatal death recorded in T group in our study. The incidence of preterm births was found to be more in NT group than T group.

Our study is consistent with the other studies in respect of LBW babies. In our study, we found the incidence of LBW babies significantly (p < 0.001) higher in T group (60%) than NT group (45.9%). Fang J et al. found that the population attributable risk of LBW in hypertensive mothers was highest among blacks and lowest among whites. They concluded that maternal hypertension is an important risk factor for LBW in New York City. Its impact, however, differed by race/ethnicity groups [72]. Odell CD et al. reported that differences in maternal risk factors and rates of LBW exist between Haitian and African-American women delivering infants in Massachusetts. While chronic hypertension and preeclampsia are strong risk factors for LBW for both Haitian and African-American women, “unknown factors” make these disorders much more potent for Haitian women [27]. Those unknown factors may be related to their race or ethnicity and this observation corroborates with our finding of higher incidence of LBW in ethnic tribals than nontribals.

In our study the admission to NICU was required in a small number of babies and the need for admission to NICU was found to be almost similar in both groups. This may be due to higher rate of delivery of asphyxiated infant and preterm babies in NT group which compensated the higher rate of SGA babies in T group.

Hypertensive disorders of pregnancy remain an important maternal health problem in India. By this comparative study, we came to a conclusion that the tribal women are at higher risk of developing severe preeclampsia and eclampsia than nontribal women.

It is well established that extremes of age and nulliparity are strong risk factors for preeclampsia-eclampsia but these factors make the tribal ethnicity more prone to the disease.

Tribal women develop more severe hypertension and are less responsive to antihypertensive treatment than nontribal women.

Rate of caesarean section is high in both tribal and non tribal women with severe preeclampsia-eclampsia but comparatively higher among nontribal women.

The mortality and need of ICU care are more in tribal mothers than nontribal mothers when they develop severe preeclampsia-eclampsia.

Low birth weight neonates are more common in tribal women than nontribals whereas birth asphyxia and preterm births are more common in nontribal women.

These significant differences among the two groups suggest a strong role for ethnicity in the risk and pathogenesis of preeclampsia-eclampsia and it warrants further studies to understand it more clearly.

More awareness among both the tribal and non tribal group and routine antenatal checkup might improve the feto-maternal outcome in these groups of individuals (Q.7).

The authors declare no conflicts of interest regarding the publication of this paper.

Banerjee, I., Kumari, A. and Mukherjee, G. (2021) Study of the Role of Ethnicity in the Pathophysiology of Preeclampsia: A Prospective Observational Study in a Rural Hospital in India. Open Journal of Obstetrics and Gynecology, 11, 978-1004. https://doi.org/10.4236/ojog.2021.118093