What do systematic reviews say?

Intervention not reported

The intervention showed no clear difference in very preterm birth (less than 34 weeks) ‐ assuming complete… (low certainty).

• Bed rest with and without hospitalisation in multiple pregnancy for improving perinatal outcomes 2017 · Cochrane Headline outcomes only
  RR 1.02 [0.66, 1.58]
  5 studies · 495 participants
  Low

Intervention not reported

The intervention showed no clear difference in very preterm birth (less than 34 weeks) ‐ assuming complete… (low certainty).

• Bed rest with and without hospitalisation in multiple pregnancy for improving perinatal outcomes 2017 · Cochrane Headline outcomes only
  RR 2.3 [0.84, 6.27]
  1 study · 141 participants
  Low

Acupuncture vs placebo

Acupuncture showed no clear difference in preterm birth less than 37 weeks compared with placebo (low certainty).

• Interventions for treating hyperemesis gravidarum 2016 · Cochrane Headline outcomes only
  RR 0.12 [0.01, 2.26]
  1 study · 36 participants
  Low

Corticosteroids vs promethazine

Corticosteroids showed no clear difference in preterm birth compared with promethazine (low certainty).

• Interventions for treating hyperemesis gravidarum 2016 · Cochrane Headline outcomes only
  RR 3 [0.13, 69.52]
  1 study · 40 participants
  Low

Corticosteroids vs placebo

It is very uncertain whether corticosteroids changes preterm birth compared with placebo (very low certainty).

• Interventions for treating hyperemesis gravidarum 2016 · Cochrane Headline outcomes only
  RR 1.01 [0.31, 3.28]
  2 studies · 134 participants
  Very low

Balanced protein and energy supplementation vs no intervention or control intervention (control)

Balanced protein and energy supplementation showed no clear difference in preterm birth compared with control or no intervention (moderate certainty).

• Antenatal dietary education and supplementation to increase energy and protein intake 2015 · Cochrane Headline outcomes only
  RR 0.96 [0.8, 1.16]
  5 studies · 3384 participants
  Moderate

Intervention not reported

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

• Antenatal dietary education and supplementation to increase energy and protein intake 2015 · Cochrane Headline outcomes only
  RR 1.14 [0.83, 1.56]
  1 study · 505 participants
  Low

Intervention not reported

• Antenatal dietary education and supplementation to increase energy and protein intake 2015 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Nutritional education vs no counselling or education during pregnancy

Nutritional education may leads to lower preterm birth compared with no counselling or education during pregnancy (low certainty).

• Antenatal dietary education and supplementation to increase energy and protein intake 2015 · Cochrane Headline outcomes only
  RR 0.46 [0.21, 0.98]
  2 studies · 449 participants
  Low

External cephalic version (ECV) commenced before term vs ECV at term

External cephalic version (ECV) commenced before term leads to higher preterm birth < 37 weeks compared with ECV at term (high certainty).

• External cephalic version for breech presentation before term 2015 · Cochrane Headline outcomes only
  RR 1.51 [1.03, 2.21]
  3 studies · 1888 participants
  High

Pyridoxine vs control

• Pyridoxine (vitamin B6) supplementation during pregnancy or labour for maternal and neonatal outcomes 2015 · Cochrane Headline outcomes only
  no estimate extracted
  0 participants
  GRADE not reported

Reduced number of antenatal care visits/goal‐oriented vs standard antenatal care visits

Reduced number of antenatal care visits/goal‐oriented showed no clear difference in preterm birth compared with standard antenatal care visits (moderate certainty).

• Alternative versus standard packages of antenatal care for low‐risk pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.02 [0.94, 1.11]
  7 studies · 53661 participants
  Moderate

All routine Doppler ultrasound vs no Doppler ultrasound

All routine Doppler ultrasound showed no clear difference in preterm birth (before 37 weeks) compared with no Doppler ultrasound (high certainty).

• Fetal and umbilical Doppler ultrasound in normal pregnancy 2015 · Cochrane Headline outcomes only
  RR 1.02 [0.86, 1.21]
  4 studies · 12162 participants
  High

Vitamin E vs placebo, no placebo or other supplements

Any vitamin E supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo, no placebo or other supplements (high certainty).

• Vitamin E supplementation in pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.98 [0.88, 1.09]
  11 studies · 20565 participants
  High

Intervention not reported

The intervention showed no clear difference in preterm birth (< 37 weeks' gestation) (high certainty).

• Vitamin C supplementation in pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.99 [0.9, 1.1]
  16 studies · 22250 participants
  High

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