An evidence review and nutritional conceptual framework for pre-eclampsia prevention.

Pre-eclampsia is a serious complication of pregnancy, and maternal nutritional factors may play protective roles or exacerbate risk. The tendency to focus on single nutrients as a risk factor obscures the complexity of possible interactions, which may be important given the complex nature of pre-eclampsia. An evidence review was conducted to compile definite, probable, possible and indirect nutritional determinants of pre-eclampsia to map a nutritional conceptual framework for pre-eclampsia prevention. Determinants of pre-eclampsia were first compiled through an initial consultation with experts. Secondly, an expanded literature review was conducted to confirm associations, elicit additional indicators and evaluate evidence. The strength of association was evaluated as definite RR<0.40 or ≥3.00, probable RR 0.40-0.69 or 1.50-2.99, possible RR 0.70-0.89 or 1.10-1.49 or not discernible RR 0.90-1.09. The quality of evidence was evaluated using GRADE. Twenty-five nutritional factors were reported in two umbrella reviews and 22 meta-analyses. Of these, 14 were significantly associated with pre-eclampsia incidence. Maternal vitamin D deficiency and higher serum iron emerged as definite nutritional risk factors for pre-eclampsia incidence across populations, while low serum zinc was a risk factor in Asia and Africa. Calcium and/or vitamin D supplementation were probable protective nutritional factors. Healthy maternal dietary patterns were possibly associated with lower risk of developing pre-eclampsia. Potential indirect pathways of maternal nutritional factors and pre-eclampsia may exist through obesity, maternal anaemia and gestational diabetes mellitus. Research gaps remain on the influence of household capacities and sociocultural, economic and political contexts, as well as interactions with medical conditions.