The association of malaria infection and gestational hypertension in Africa: Systematic review and meta-analysis

Background: The World Health Organisation (WHO) estimates that hypertensive disorders of pregnancy (HDP) contribute 14% to global maternal mortality. HDP encompasses several subcategories, including gestational hypertension (GH) and pre-eclampsia. These two conditions are both characterised by a rise in blood pressure, with an onset from 20 weeks of gestation. They also share some common risk factors. The current definition of pre-eclampsia includes raised blood pressure in the absence of proteinuria, thus presenting the two conditions as a spectrum. In this article, we refer to both conditions as gestational hypertension, which is our outcome of interest. The aetiology of GH is not yet clearly understood. Observational studies have suggested that malaria may be associated with GH. However, the evidence from these small studies has been inconclusive. Having a better understanding of the association between malaria and GH may help inform prevention strategies to reduce maternal and infant mortality and morbidity.

Methods: In assessing the association between malaria infection and GH we explored open access articles published in the English language on Medline, Embase, WHO GIM and Google scholar. The subject related articles were retrieved and processed according to preferred reporting items in systematic reviews and meta-analyses (PRISMA) guidelines. Search date was 9th week of 2018. Inverse variance weighting method in Revman 5 software (Cochrane Collaboration, London, United Kingdom) was used to aggregate evidence by computing the pooled odds ratio to show the nature and strength of the relationship between malaria and GH.

Results: Using critical appraisal skills program (CASP) checklist tool we identified four good quality case-control studies. The total sample size was 1281 women out of which 518 were cases. These studies together show malaria is associated with GH with an overall odds ratio of 2.67, 95% confidence interval (CI) = 1.58-4.53. Heterogeneity of the individual studies supported fixed effect modelling assumptions (I2 = 0%). Malaria infection may have a constant effect on GH across different African populations. The funnel plot did not suggest publication bias however, the four studies involved in the meta-analysis were insufficient to rule it out.

Conclusions: Our findings provide evidence of an association between malaria infection and gestational hypertension; this underscores the need to control malaria especially during pregnancy.