Introduction: Preeclampsia is a complex hypertensive disorder diagnosed during pregnancy, ≥ 20 weeks’ gestation. Collectively, preeclampsia and eclampsia account for one-third of severe maternal morbidities and are responsible for 10–15% of maternal mortality rates, predominantly in low to middle-income countries. While the pathogenesis of preeclampsia remains unclear, multiple studies suggest aetiology may stem from a combination of several complex, multifactorial interactions, including genetic and environmental causes. Few studies report on the global incidence or prevalence of preeclampsia, nor examine specific risk factors within individual nations, including Aotearoa/New Zealand. Moreover, due to reliance on now outdated diagnostic criteria, under-reporting of rates of preeclampsia is likely.
Aim: This research aims to 1) describe the incidence and prevalence of preeclampsia both globally and nationally, and 2) identify any environmental, geographical, cultural and socio-economic factors that may be associated with preeclampsia incidence and prevalence in Aotearoa/New Zealand. All primary research studies and other relevant published literature informing the topic between January 2010 and August 2020 will be critiqued and evaluated; in particular, those meeting with cross-sectional, cohort or systematic review criteria.

Method: The quantitative method of an integrative review was selected as the most suitable for an extensive critique and analysis of international and national literature available over the past decade which commented on the mapping of the global incidence and prevalence of preeclampsia, while identifying emergent themes of interest. Key word searches will be undertaken within the Wintec ‘OneSearch’ library access of major data bases, including (but not limited to) CINAHL Complete, Clinical Trials, Directory of Open Access Journals, Gale Academic One File, PLOS/ONE and Science Direct. Articles not relating specifically to preeclampsia incidence and/or prevalence will be excluded along with any duplicates, articles not available in English, and those involving animal rather than human participants. By assessing many forms of research, the existing body of knowledge can be evaluated and future areas for interest and research potential ascertained.

Results: Following analysis of six multi-database keyword searches identifying 2833 potential articles for review, the search was limited to include academic journals only and studies undertaken between January 2015 and August 2020, in order to attempt to exclude those drawing on pre-2014 diagnostic criteria for preeclampsia requiring manifestation of proteinuria. Once duplicates were excluded, abstracts were then analysed for potential inclusion. Keyword search six was abandoned due to a significant number of identified duplicates. Those making no specific reference to incidence or prevalence of preeclampsia were also excluded. In total, 64 studies from around the globe were included in the final review analysis and examined in full-text PDF format. Many studies published beyond 2015 continued to apply outdated diagnostic criteria for preeclampsia or failed to report their countries overall incidence and/or prevalence of preeclampsia. Other studies that later re-evaluated their findings in line with the revised 2014 International Society for the Study of Hypertension in Pregnancy Guidelines noted higher incidence of preeclampsia once new criteria were applied. Many studies attributed the incidence of preeclampsia to poverty, delayed and/or inaccurate diagnosis, limited health resources, or inequitable access to those that were available; however, this aspect needs further and more in-depth exploration. There were no studies originating from Aotearoa/New Zealand that met with inclusion criteria, meaning scope for future research within this context is warranted.

Conclusion: Globally and within Aotearoa/New Zealand, incidence and prevalence of preeclampsia cannot be determined in exact measures, due largely to limitations in reporting, and the potential for missed diagnosis due to use of conflicting diagnostic criteria. Additionally, further examination and assessment of factors such as environmental, geographical, cultural, and social considerations which may influence and/or impact on the incidence and prevalence of preeclampsia, both globally and within an Aotearoa/New Zealand framework, should be comprehensively explored and evaluated.