What do systematic reviews say?

Vitamin E + vitamin C vs placebo

Vitamin C and vitamin E showed no clear difference in total fetal loss compared with placebo (high certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 1.14 [0.92, 1.4]
  7 studies · 18949 participants
  High

Vitamin E + vitamin C vs placebo

Vitamin C and vitamin E showed no clear difference in early or late miscarriage compared with placebo (moderate certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 0.9 [0.65, 1.26]
  4 studies · 13346 participants
  Moderate

Vitamin E + vitamin C vs placebo

Vitamin C and vitamin E showed no clear difference in stillbirth compared with placebo (moderate certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 1.31 [0.97, 1.76]
  7 studies · 21442 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 + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

It is very uncertain whether vitamin D + calcium + other vitamins and minerals changes gestational diabetes compared with calcium + other vitamins and minerals (but no vitamin D) (very low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.42 [0.1, 1.73]
  1 study · 1298 participants
  Very low

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
  1 study · 1298 participants
  Very low

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
  1 study · 1298 participants
  Very low

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

Vitamin D + calcium + other vitamins and minerals showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with calcium + other vitamins and minerals (but no vitamin D) (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.04 [0.68, 1.59]
  1 study · 1298 participants
  Low

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

Vitamin D + calcium + other vitamins and minerals showed no clear difference in low birthweight (less than 2500 g) compared with calcium + other vitamins and minerals (but no vitamin D) (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.12 [0.82, 1.51]
  1 study · 1298 participants
  Low

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 33 participants
  Very low

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 33 participants
  Very low

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… showed no clear difference in low birthweight (less than 2500 g) compared with daily regimen (with same vitamins and minerals)‐infant outcomes (low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.82 [0.55, 1.22]
  8 studies · 1898 participants
  Low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

It is very uncertain whether any intermittent iron regimen (with or without other vitamins and… changes side effects (any reported throughout intervention period) compared with daily regimen (with same vitamins and minerals)‐maternal outcomes (very low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.56 [0.37, 0.84]
  11 studies · 1777 participants
  Very low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  no estimate extracted
  6 studies · 1240 participants
  Very low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… led to lower maternal clinical malaria or other infection in pregnancy compared with daily regimen (with same vitamins and minerals)‐maternal outcomes; GRADE not reported.

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0 [0, 0]
  0 studies · 0 participants
  GRADE not reported

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… showed no clear difference in birthweight (g) compared with daily regimen (with same vitamins and minerals)‐infant outcomes (low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  MD 5.13
  9 studies · 1939 participants
  Low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… showed no clear difference in premature birth (less than 37 weeks of gestation) compared with daily regimen (with same vitamins and minerals)‐infant outcomes (low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.03 [0.76, 1.39]
  5 studies · 1177 participants
  Low