What do systematic reviews say?

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

(Maternal outcomes) Any supplements containing iron may leads to lower maternal iron deficiency at term (as defined by as defined by… compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.43 [0.27, 0.66]
  7 studies · 1256 participants
  Low

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

(Maternal outcomes) Any supplements containing iron and folic acid may leads to lower maternal iron deficiency at term (as defined by trialists, based on… compared with same supplements without iron nor folic acid (no iron nor folic acid… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.24 [0.06, 0.99]
  1 study · 131 participants
  Low

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 severe anaemia at any time during second and third… 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 0.22 [0.01, 3.2]
  9 studies · 2125 participants
  Very low

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 side effects (any reported throughout the intervention period) (ALL) 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 1.29 [0.83, 2.02]
  11 studies · 2423 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)

(Maternal outcomes) Any supplements containing iron and folic acid probably leads to higher side effects (any reported throughout the intervention period) (ALL) compared with same supplements without iron nor folic acid (no iron nor folic acid… (moderate certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 44.32 [2.77, 709.09]
  1 study · 456 participants
  Moderate

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

It is very uncertain whether (Maternal outcomes) Any supplements containing iron and folic acid changes maternal severe anaemia at any time during second and third… compared with same supplements without iron nor folic acid (no iron nor folic acid… (very low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.12 [0.02, 0.63]
  4 studies · 506 participants
  Very low

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

(Infant outcomes) Any supplements containing iron showed no clear difference in low birthweight (less than 2500 g) (ALL) compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.84 [0.69, 1.03]
  11 studies · 17613 participants
  Low

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

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  no estimate extracted
  15 studies · 18590 participants
  Moderate

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

(Infant outcomes) Any supplements containing iron showed no clear difference in preterm birth (less than 37 weeks of gestation) (ALL) compared with same supplements without iron or no treatment/placebo (no iron or… (moderate certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.93 [0.84, 1.03]
  13 studies · 19286 participants
  Moderate

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

(Infant outcomes) Any supplements containing iron showed no clear difference in neonatal death (within 28 days after delivery) (ALL) compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.91 [0.71, 1.18]
  4 studies · 16603 participants
  Low

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

(Infant outcomes) Any supplements containing iron showed no clear difference in congenital anomalies (ALL) compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.88 [0.58, 1.33]
  4 studies · 14636 participants
  Low

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

(Maternal outcomes) Any supplements containing iron showed no clear difference in infection during pregnancy (including urinary tract infections) (ALL) compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.21 [0.33, 4.46]
  1 study · 727 participants
  Low

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

(Maternal outcomes) Any supplements containing iron may leads to lower maternal anaemia at term (Hb less than 110 g/L at 37 weeks'… compared with same supplements without iron or no treatment/placebo (no iron or… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.3 [0.19, 0.46]
  14 studies · 2199 participants
  Low

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)

(Infant outcomes) Any supplements containing iron and folic acid showed no clear difference in low birthweight (less than 2500 g) (ALL) compared with same supplements without iron nor folic acid (no iron nor folic acid… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.07 [0.31, 3.74]
  2 studies · 1311 participants
  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
  2 studies · 1365 participants
  Moderate

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

(Infant outcomes) Any supplements containing iron and folic acid showed no clear difference in preterm birth (less than 37 weeks of gestation) (ALL) compared with same supplements without iron nor folic acid (no iron nor folic acid… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.55 [0.4, 6]
  3 studies · 1497 participants
  Low

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

(Infant outcomes) Any supplements containing iron and folic acid showed no clear difference in neonatal death (within 28 days after delivery) (ALL) compared with same supplements without iron nor folic acid (no iron nor folic acid… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.81 [0.51, 1.3]
  3 studies · 1793 participants
  Low

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

(Infant outcomes) Any supplements containing iron and folic acid showed no clear difference in congenital anomalies (ALL) compared with same supplements without iron nor folic acid (no iron nor folic acid… (low certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.7 [0.35, 1.4]
  1 study · 1652 participants
  Low

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

(Maternal outcomes) Any supplements containing iron and folic acid probably leads to lower maternal anaemia at term (Hb less than 110 g/L at 37 weeks'… compared with same supplements without iron nor folic acid (no iron nor folic acid… (moderate certainty).

• Daily oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.34 [0.21, 0.54]
  3 studies · 346 participants
  Moderate