Hypertensive disorders in pregnancy are one of the leading causes of morbidity, long-term disability and death during pregnancy and postpartum and account for approximately 14% of all maternal deaths worldwide . Hypertensive disorders of pregnancy include: chronic hypertension; gestational hypertension; pre-eclampsia with or without severe features; eclampsia and chronic hypertension with superimposed pre-eclampsia [2, 3]. Hypertensive disorders are the second leading cause of maternal mortality worldwide . A useful framework for understanding causes of maternal deaths includes the three delays model; 1) delay in deciding to seek care, 2) delay in reaching a healthcare facility 3) delay in receiving appropriate and correct care at the healthcare facility . A woman with an obstetric emergency may delay seeking health care services because she does not know the complications and risk factors in pregnancy; she might have history of bad experience of health care; financial implications. The woman who have decided early and timely to seek health care may find obstacles in reaching the health facility as transport is limited in may settings. Upon arrival, she may experience a delay in receiving appropriate care because the health facilities lacks materials and supplies for her care and/or care providers are not optimally trained . Each of these three delays impacts the morbidity and mortality among women with obstetric emergencies, including hypertensive disorders of pregnancy.
Pre-eclampsia complicates 2–8% of pregnancies globally and in Africa and Asia 9% of maternal deaths are attributed to pre-eclampsia . From a global perspective, most deaths due to hypertensive disorders of pregnancy occur in developing countries . The World Health Organization (WHO) estimates the incidence of pre-eclampsia in developing countries seven times higher (2.8% of live births) compared to more developed countries (0.4%) . Pre-eclampsia is a multisystemic disorder of pregnancy associated with new-onset hypertension, which occurs most often after 20 weeks of gestation and frequently near term  with the presence of proteinuria or, in its absence, of signs or symptoms indicative of target organ injury . Pre-eclampsia is categorized as being with or without severe features .
High resource countries classify pre-eclampsia with severe features with specific criteria. This includes new-onset severe range blood pressures (sBP) ≥ 160 mmHg or diastolic BP (dBP) ≥ 110 mmHg with or without proteinuria. Specific laboratory findings are also present with severe features including thrombocytopenia (platelet count less than 100,000 × 109/L), impaired liver function as indicated by abnormally elevated blood concentrations of liver enzymes (to twice the upper limit normal concentration), and severe persistent right upper quadrant or epigastric pain unresponsive to medication and not accounted for by alternative diagnoses, renal insufficiency (serum creatinine concentration more than 1.1 mg/dL or a doubling of the serum creatinine concentration in the absence of other renal disease) pulmonary edema, new-onset headache unresponsive to medication and not accounted for by alternative diagnoses, or visual disturbances [2, 6]. In high resource settings, this type of clear classification of pre-eclampsia is more feasible. In contrast, many low resources settings do not have lab testing available nor have functioning equipment for blood pressure measurement. This makes diagnosis of pre-eclampsia a particular challenge in such settings. Often in low resource settings, health providers rely on a combination of blood pressure elevation plus clinical findings to make a diagnosis of pre-eclampsia with severe features. Often pre-eclampsia is not diagnosed and pregnant women present emergently with eclamptic seizures. Given high maternal mortality rates in low resource settings, the impact of pre-eclampsia is significant. In Sub-Saharan Africa alone, pre-eclampsia remains a major public health problem as the reported the prevalence of pre-eclampsia ranges from 1.8 to 16.7% and contributes to high rates of maternal mortality .
The adverse effects of severe pre-eclampsia have been reported in the literature, for example a study conducted on characteristics and outcomes of patient with eclampsia and pre-eclampsia in a rural hospital in Tanzania demonstrated a significant impact on neonates. In this study, 27% of perinatal deaths occurred among women with severe pre-eclampsia. In addition, more than one-third of neonates had a birth weight of less than 2.5kgs and 86% had birth weight less than 1.5kgs . Furthermore, the study demonstrated that 38% of low birth weight babies did not survive and that poor neonatal outcomes were associated with long durations between admission time and delivery [4, 5].
The World Health Organization on its recommendations for prevention and treatment of pre-eclampsia and eclampsia identified key risks of obesity, chronic hypertension, diabetes, nulliparity, adolescent pregnancy and conditions leading to hyper-placentation and large placentas (e.g. twin pregnancy), previous pre-eclampsia, renal disease, autoimmune disease and multiple pregnancies . Furthermore, risk factors for pre-eclampsia have been widely reported in sub-Saharan Africa, example is a retrospective study conducted at Kilimanjaro Christian Medical Center on prevalence and risk factors of pre-eclapsia and eclampsia, the factors including maternal age (≥35) years, ≥12 years of schooling, unmarried, overweight, obesity, hypertension and anaemia . Moreover, obesity was reported as a risk factor for severe pre-eclampsia among sub-Sahan Africa women immigrated to Europe . More literature have reported age 40 years or older, a pregnancy interval of more than 10 years, family history of pre-eclampsia, BMI of 35 kg/m2 or more, gestational age at presentation and pre-existing vascular disease (NICE, 2019).
Despite various efforts taken by the Tanzanian government in Zanzibar, it has a high maternal mortality rate of 647/100,000 live births with hemorrhage and hypertensive disorders as the leading causes of direct maternal death in Zanzibar [10, 11]. In Zanzibar, a study conducted at Mnazi Mmoja Referral Hospital revealed hypertensive disorders in pregnancy as the most frequent complication in all pregnancies, whereby severe pre-eclampsia was reported in 25.8% of potential life-threatening conditions and 13.5% of maternal near-miss events. Furthermore, the study found that severe pre-eclampsia contribute about 21.4% of maternal deaths .
In this study, the definition of severe pre-eclampsia included having gestational hypertension with severe range of blood pressure systolic blood pressure >160 mmHg and diastolic >110 mmHg urine with protein (proteinuria), swelling of face and extremities or generalized edema, blurred vision, severe headache, severe persistent right upper quadrant or epigastric pain unresponsive to medication and not accounted for by alternative diagnosis, or pulmonary edema. Classifying pre-eclampsia is important for delivery timing, as delivery is the treatment for pre-eclampsia. This study therefore sought to assess the prevalence and risk factors of severe pre-eclampsia among postpartum women in Zanzibar.