What do systematic reviews say?

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 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

Specialised antenatal clinics vs usual care

The review found no eligible studies for this question.

• Specialised antenatal clinics for women with a multiple pregnancy for improving maternal and infant outcomes 2015 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Intervention not reported

The intervention showed no clear difference in preterm birth (< 37 weeks gestation) (Any psychosocial intervention… (moderate certainty).

• Psychosocial interventions for pregnant women in outpatient illicit drug treatment programs compared to other… 2015 · Cochrane Headline outcomes only
  RR 0.71 [0.34, 1.51]
  3 studies · 264 participants
  Moderate

Caffeinated (experimental group) vs decaffeinated group (control group)

Caffeinated (experimental group) showed no clear difference in preterm birth compared with decaffeinated group (control group) (low certainty).

• Effects of restricted caffeine intake by mother on fetal, neonatal and pregnancy outcomes 2015 · Cochrane Headline outcomes only
  RR 0.81 [0.48, 1.37]
  1 study · 1153 participants
  Low

Calcium supplementation/fortification vs placebo or no intervention

Calcium supplementation showed no clear difference in preterm birth (a) Birth prior to 37 weeks compared with placebo or no treatment (maternal outcomes) (moderate certainty).

• Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes 2015 · Cochrane Headline outcomes only
  RR 0.86 [0.7, 1.05]
  13 studies · 16139 participants
  Moderate

Calcium supplementation/fortification vs placebo or no intervention

Calcium supplementation showed no clear difference in preterm birth (b) Birth prior to 34 weeks compared with placebo or no treatment (maternal outcomes) (moderate certainty).

• Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes 2015 · Cochrane Headline outcomes only
  RR 1.04 [0.8, 1.36]
  4 studies · 5669 participants
  Moderate

All diet and/or exercise interventions vs (Optimised) usual care

All diet and/or exercise interventions showed no clear difference in preterm birth compared with standard/other care (moderate certainty).

• Diet or exercise, or both, for preventing excessive weight gain in pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.91 [0.68, 1.22]
  16 studies · 5923 participants
  Moderate

Group antenatal care vs individual antenatal care (adjusted data)

Group antenatal care showed no clear difference in preterm birth (gestational age at time of birth less than 37 weeks'… compared with individual antenatal care (adjusted data) (moderate certainty).

• Group versus conventional antenatal care for women 2015 · Cochrane Headline outcomes only
  RR 0.75 [0.57, 1]
  3 studies · 1888 participants
  Moderate

Intervention not reported

The intervention showed no clear difference in preterm birth (low certainty).

• Vitamin A supplementation during pregnancy for maternal and newborn outcomes 2015 · Cochrane Headline outcomes only
  RR 0.39 [0.08, 1.93]
  1 study · 136 participants
  Low

Vitamin A vs placebo or no treatment

Vitamin A alone showed no clear difference in preterm birth compared with placebo or no treatment (high certainty).

• Vitamin A supplementation during pregnancy for maternal and newborn outcomes 2015 · Cochrane Headline outcomes only
  RR 0.98 [0.94, 1.01]
  5 studies · 48007 participants
  High

Nitrofurantoin and close surveillance vs close surveillance alone

It is very uncertain whether nitrofurantoin and close surveillance changes preterm birth (< 37 weeks) compared with close surveillance alone (very low certainty).

• Interventions for preventing recurrent urinary tract infection during pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.18 [0.42, 3.35]
  1 study · 147 participants
  Very low

Home (point‐of‐use) fortification of foods with multiple micronutrient powders vs multiple micronutrients (MMN)

• Multiple micronutrient powders for home (point‐of‐use) fortification of foods in pregnant women 2015 · Cochrane Headline outcomes only
  no estimate extracted
  0 participants
  GRADE not reported

Home (point‐of‐use) fortification of foods with multiple micronutrient powders vs iron folic acid (IFA)

• Multiple micronutrient powders for home (point‐of‐use) fortification of foods in pregnant women 2015 · Cochrane Headline outcomes only
  no estimate extracted
  0 participants
  GRADE not reported

Test of placental function vs usual care

Test of placental function showed no clear difference in preterm birth (before 37 weeks' gestation) reported gestation at birth compared with standard care (low certainty).

• Use of biochemical tests of placental function for improving pregnancy outcome 2015 · Cochrane Headline outcomes only
  RR 2.9 [0.12, 69.81]
  1 study · 118 participants
  Low

Universal screening vs No screening

The review found no eligible studies for this question.

• Screening and subsequent management for thyroid dysfunction pre‐pregnancy and during pregnancy for improving maternal… 2015 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Universal screening vs case finding

Universal screening showed no clear difference in preterm birth compared with case finding (high certainty).

• Screening and subsequent management for thyroid dysfunction pre‐pregnancy and during pregnancy for improving maternal… 2015 · Cochrane Headline outcomes only
  RR 0.99 [0.8, 1.24]
  1 study · 4516 participants
  High

Intervention not reported

The intervention showed no clear difference in preterm birth (low certainty).

• Drugs for preventing malaria in pregnant women in endemic areas: any drug regimen versus placebo or no treatment 2014 · Cochrane Headline outcomes only
  RR 0.85 [0.66, 1.1]
  2 studies · 1493 participants
  Low

Intervention not reported

• Drugs for preventing malaria in pregnant women in endemic areas: any drug regimen versus placebo or no treatment 2014 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Intervention not reported

The intervention showed no clear difference in preterm birth (low certainty).

• Drugs for preventing malaria in pregnant women in endemic areas: any drug regimen versus placebo or no treatment 2014 · Cochrane Headline outcomes only
  RR 0.95 [0.65, 1.38]
  2 studies · 1174 participants
  Low