Table 1. Characteristics of studies included in this systematic review.
ADA = American Diabetes Association; GDM = gestational diabetes mellitus; BMI = body mass index; CRP = C‐reactive protein; WHO = World Health Organization; IADPSG = International Association of Diabetes and Pregnancy Study Groups; sTfR = serum transferrin receptor; TIBC = total iron-binding capacity; PIH = pregnancy-induced hypertension; LDL = low-density lipoprotein.
| Authors | Year | Location | Study design | Sample size | Diagnosis of GDM | Trimester for biomarker collection | Iron indices | Variables adjustment |
| Yadav et al. [22] | 2017 | India | Case-control | 30/60 | Carpenter and Coustan criteria | Second | Serum ferritin | Obesity and history of infection |
| Soheilykhah et al. [23] | 2017 | Iran | Prospective cohort | 1279 | WHO | First | Serum ferritin, iron, hemoglobin, TIBC | Age, level of education, reproductive medical history |
| Bowers et al. [24] | 2016 | Denmark | Prospective cohort | 350/349 | WHO | First | Serum ferritin, sTfR, heme and non-heme dietary iron, iron supplement | Family history of diabetes, BMI, age, parity, CRP, oxidized LDL |
| Rawal et al. [25] | 2017 | USA | Case-control | 107/321 | WHO | First | Serum ferritin, sTfR, CRP | Age ethnicity, parity, education, smoking, alcohol, BMI, family history of diabetes |
| Khambalia et al. [26] | 2015 | Australia | Prospective cohort | 3776 | Unexplained | First | Serum ferritin, sTfR, CRP | Age, country of birth, BMI, smoking, PIH |
| Zein et al. [27] | 2015 | Lebanon | Prospective cohort | 16/88 | WHO and IADPSG | First | Serum ferritin, hemoglobin CRP | Age, BMI, education level, previous cesarean/miscarriage |
| Amiri et al. [28] | 2013 | Iran | Case-control | 100/100 | Carpenter and Coustan criteria | Second | Serum ferritin iron TIBC | Age, parity, body mass index, gestational age |
| Behboudi-Gandevani et al. [29] | 2013 | Iran | Prospective cohort | 72/961 | Carpenter and Coustan criteria | Second | Serum Iron, hemoglobin, total dietary iron | Age, BMI, education, job, parity, family history of GDM |
| Javadian et al. [30] | 2014 | Iran | Case-control | 52/20 | ADA,14 | Second | Ferritin, hemoglobin | Gestational age, maternal age, weight |
| Helin et al. [31] | 2012 | Finland | Prospective cohort | 68/321 | Carpenter and Coustan criteria | First | Iron intake, hemoglobin | Maternal age and weight, total maternal weight gain, family history of diabetes, previous gestational diabetes or macrosomia, total calories intake, fiber, and saturated fatty acids intake |