What do systematic reviews say?

Any supplements containing iron vs same supplements without iron or no treatment/placebo (no iron or placebo)

It is very uncertain whether (Maternal outcomes) Any supplements containing iron changes maternal death (death while pregnant or within 42 days of… compared with same supplements without iron or no treatment/placebo (no iron or… (very low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.33 [0.01, 8.19]
  2 studies · 12560 participants
  Very low

Any supplements containing iron and folic acid vs same supplements without iron nor folic acid (no iron nor folic acid or placebo)

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 131 participants
  Low