What do systematic reviews say?

Vitamin E vs placebo, no placebo or other supplements

Any vitamin E supplementation showed no clear difference in clinical pre‐eclampsia (random‐effects model) compared with placebo, no placebo or other supplements (moderate certainty).

• Vitamin E supplementation in pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.91 [0.79, 1.06]
  14 studies · 20878 participants
  Moderate

Vitamin D + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Vitamin D vs placebo or no intervention

Vitamin D supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.48 [0.3, 0.79]
  4 studies · 499 participants
  Moderate

Vitamin D plus calcium vs placebo or no intervention

Vitamin D + calcium supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.5 [0.32, 0.78]
  4 studies · 1174 participants
  Moderate

A dose of vitamin D 601 IU or higher vs 600 IU or lower alone or with other nutrients

A dose of vitamin D 601 IU or higher showed no clear difference in pre‐eclampsia compared with 600 IU or lower alone or with other nutrients (low certainty).

• Regimens of vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.96 [0.65, 1.42]
  5 studies · 1553 participants
  Low

A dose of vitamin D 4000 IU/d or more vs 3999 IU/d or less alone or with any other nutrient

A dose of vitamin D 4000 IU/d or more showed no clear difference in pre‐eclampsia compared with 3999 IU/d or less alone or with any other nutrient (low certainty).

• Regimens of vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.87 [0.62, 1.22]
  4 studies · 1903 participants
  Low

Intervention not reported

The intervention showed no clear difference in clinical pre‐eclampsia (moderate certainty).

• Vitamin C supplementation in pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.92 [0.8, 1.05]
  16 studies · 21956 participants
  Moderate

Pyridoxine vs control

Pyridoxine (B6) showed no clear difference in pre‐eclampsia ‐ Antenatal oral pyridoxine versus control compared with control (low certainty).

• Pyridoxine (vitamin B6) supplementation during pregnancy or labour for maternal and neonatal outcomes 2015 · Cochrane Headline outcomes only
  RR 1.71 [0.85, 3.45]
  2 studies · 1197 participants
  Low
• Pyridoxine (vitamin B6) supplementation during pregnancy or labour for maternal and neonatal outcomes 2015 · Cochrane Headline outcomes only
  RR 1.43 [0.64, 3.22]
  1 study · 944 participants
  Low