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Table 2 Characteristics of included reports

From: The role of vitamin D in pre-eclampsia: a systematic review

Author, Location, Year Design Subjects Time of vitamin D measurement
Cross-Sectional Studies
 August et al., USA, 1992 [88] Cross-sectional 11 – women with PE 3rd trimester
9 – chronic HTN
12 – normotensive pregnant controls
 Fernandez- Alonzo et al., Spain, 2012 [97] Cross-sectional 466 – pregnant women (7 had PE) 1st trimester
 Pena HR, et al. Brazil 2015 [83] Cross-sectional 179 -- pregnant women recruited before delivery Near delivery
Case Control Studies
 Abedi et al., Iran, 2014 [84] Case Control 59 – women with PE At delivery
59 – healthy pregnant controls
 Achkar et al., Canada, 2015 [81] Case Control 169 – women with PE <20 weeks gestation
1975 – healthy pregnant controls
 Anderson et al., USA, 2015 [111] Case control 11 -- gestational HTN (10/11 with PE) At delivery
37 – healthy pregnant controls
 Baker et al., 2010 [80] Nested Case Control 51 – developed PE 2nd trimester
204 – healthy pregnant controls
 Bodnar et al., USA, 2007 [18] Nested Case Control 55 – developed PE <22 weeks
219 – healthy pregnant controls
 Bodnar et al., USA, 2014 [79] Case Control 717 – developed PE <26 weeks gestation
560 mild; 157 severe
2986 – healthy pregnantcontrols
 Gidlof S, et al. Sweden, 2015 [112] Nested Case Control 39 – developed preeclampsia 12th week of gestation
120 – healthy pregnant controls
 Halhali, Mexico, 2004 [95] Case Control 10 -- developed PE, 40 – healthy pregnant controls Median 20.7 weeks gestation
 Halhali et al., Mexico, 2007 [113] Case Control 26 -- women with PE 26 – healthy pregnant controls 3rd trimester
 Lechtermann C, et al. Germany, 2–14 [85] Case Control 20 – women with PE At delivery
43 – healthy pregnant controls
 Mohaghegh et al., Iran, 2015 [89] Case Control 41 -- women with PE 50 – healthy pregnant controls Time of labor
 Powe, USA, 2010 [86] Nested Case Control 39 -- developed PE 131 – healthy pregnant controls 1st trimester
 Robinson et al., USA, 2010 [25] Case Control 50 -- women with EOSPE 29 weeks gestation
100 – healthy pregnant controls
 Schneuer et al., Australia, 2014 [114] Nested Case Control 5109 pregnant women (223 with PE and 29/223 with EOSPE) 10–14 weeks gestation
 Singla et al., India, 2015 [87] Case Control 74 -- nulliparous women with PE >30 weeks gestation
100 -- healthy nulliparous controls
 Ullah et al., Bangladesh, 2013 [82] Case Control 33 -- women with PE >20 weeks gestation
79 – normal pregnancy controls
 Wetta et al., UK, 2013 [96] Case Control 100 -women with PE 15–21 weeks gestation
200 – healthy pregnant controls
 Woodham et al., USA, 2011 [15] Nested Case Control 41 – women with severe PE 2nd Trimester
121 – uncomplicated birth controls
 Xu et al., USA, 2014 [53] Case Control 100 – women with PE ≤ 24 weeks gestation
100 – uncomplicated birth controls
 Yu et al., UK, 2012 [115] Case Control 60 –late PE 11–13 weeks gestation
30 –early PE
1000 – healthy controls
Retrospective Cohort Study
 Alvarez-Fernandez et al., Spain, 2014 [90] Retrospective Cohort 257 -- women attending obstetric triage with suspicion of PE 1st Trimester and 20 weeks of gestation
 Scholl et al., USA, 2013 [78] Retrospective cohort 1141 -- low income and minority pregnant women Entry to care (mean 13.7 ± 5.7 weeks)
Prospective Cohort Studies
 Burris et al., USA, 2014 [94] Prospective Cohort 1591 -- pregnant women 16.4–36.9 weeks gestation
 Haugen et al., Norway, 2000 [77] Prospective Cohort 23,423 -- pregnant women Vitamin D intake at weeks 15, 22, and 30 gestation
 Shand et al., Canada, 2010 [37] Prospective cohort 221 -- women at risk for PE 10–20 weeks gestation
 Wei et al., Canda 2012 [60] Prospective Cohort 697 -- pregnant women receiving vitamin C and E supplementation for the prevention of PE 12–18 weeks gestation, 24-26 weeks gestation
 Wei, Canada, 2013 [14] Prospective Cohort 697 -- pregnant women receiving vitamin C and E supplementation for the prevention of PE 24–26 weeks gestation
 Zhou, China, 2014 [116] Prospective Cohort 74 – women with PE 16–20 weeks gestation