Iron salts, high levels of hemoglobin and ferritin in pregnancy, and development of gestational diabetes : a systematic review

Abstract

Objective The aim of this study was to systematically review literature on the use of iron supplements (not including iron derived from diet), increased levels of hemoglobin and/or ferritin, and the risk of developing gestational diabetes mellitus (GDM). Data source The following databases were searched, from the study’s inception to April 2021: PUBMED, Cochrane, Web of Science, Scopus, Embase, Cinahl and Lilacs. Selection of studies A total of 6,956 titles and abstracts were reviewed, 9 of which met the final inclusion criteria, with 7,560 women in total. Data collection Data extraction was performed by two independent reviewers and disagreements were resolved by a third researcher. Data synthesis Methodological quality in controlled trials were assessed according to the Cochrane Collaboration tools (ROB-2 and ROBINS-1) and for the observational studies, the National Institutes of Health’s (NIH) quality assessment tool was used. Among the 5 observational studies, women with a higher hemoglobin or ferritin level were more likely to develop GDM when compared with those with lower levels of these parameters. Among the 3 randomized clinical trials, none found a significant difference in the incidence of GDM among women in the intervention and control groups. However, we identified many risks of bias and greatmethodological differences among them. Conclusion Based on the studies included in this review, and due to the important methodological problems pointed out, more studies of good methodological quality are needed to better establish the association between iron supplementation and GDM.

Objetivo O objetivo deste estudo foi revisar sistematicamente a literatura sobre o uso de suplementos de ferro (não incluindo o ferro derivado da dieta), aumento dos níveis de hemoglobina e/ou ferritina e o risco de desenvolver diabetes mellitus gestacional (DMG). Fontes dos dados as bases de dados PUBMED, Cochrane, Web of Science, Scopus, Embase, Cinahl e Lilacs foram pesquisadas até abril de 2021. Seleção dos estudos Foram revisados 6.956 títulos e resumos, dos quais 9 preencheram os critérios finais de inclusão, totalizando 7.560 mulheres. Coleta de dados A extração de dados foi realizada por dois revisores independentes e as divergências foram resolvidas por um terceiro revisor. Síntese dos dados A qualidade metodológica dos ensaios controlados foi avaliada de acordo comas ferramentas da Colaboração Cochrane (ROB-2 e ROBINS-1) e para os estudos observacionais, foiutilizada a ferramenta deavaliaçãodequalidadedoNational Institutes of Health (NIH). Entre os 5 estudos observacionais, as mulheres com maiores níveis de hemoglobina ou ferritina apresentaram maior probabilidade de desenvolver DMG quando comparadas àquelas com níveis mais baixos nesses parâmetros. Entre os 3 ensaios clínicos randomizados, nenhumdeles encontrou diferença significativa na incidência deDMGentre as mulheres dos grupos de intervenção e controle. No entanto, identificamosmuitos riscos de viés e enormes diferenças metodológicas entre eles. Conclusão Com base nos estudos incluídos nesta revisão e devido aos importantes problemas metodológicos apontados, são necessários mais estudos de boa qualidade metodológica paramelhor estabelecer a associação entre suplementação de ferro e DMG.