What do systematic reviews say?

Vaginal progesterone vs no treatment or placebo

Vaginal progesterone showed no clear difference in preterm birth less than 37 weeks compared with no treatment or placebo (moderate certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.97 [0.89, 1.06]
  6 studies · 1597 participants
  Moderate

Vaginal progesterone vs no treatment or placebo

Vaginal progesterone showed no clear difference in preterm birth less than 28 weeks compared with no treatment or placebo (low certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.53 [0.79, 2.97]
  3 studies · 1345 participants
  Low

Intramuscular (IM) progesterone vs no treatment or placebo

Intramuscular (IM) progesterone may leads to higher preterm birth less than 34 weeks compared with no treatment or placebo (low certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.54 [1.06, 2.26]
  2 studies · 399 participants
  Low

Intramuscular (IM) progesterone vs no treatment or placebo

Intramuscular (IM) progesterone showed no clear difference in preterm birth less than 28 weeks compared with no treatment or placebo (moderate certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.08 [0.75, 1.55]
  5 studies · 1920 participants
  Moderate

Intramuscular (IM) progesterone vs no treatment or placebo

Intramuscular (IM) progesterone showed no clear difference in preterm birth less than 37 weeks compared with no treatment or placebo (high certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.05 [0.98, 1.13]
  5 studies · 2010 participants
  High

Vaginal progesterone vs no treatment or placebo

Vaginal progesterone showed no clear difference in preterm birth less than 34 weeks compared with no treatment or placebo (low certainty).

• Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.9 [0.66, 1.23]
  5 studies · 1503 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

Lower genital tract infection screening vs No screening

Lower genital tract infection screening probably leads to lower preterm birth less than 37 weeks compared with no screening (moderate certainty).

• Antenatal lower genital tract infection screening and treatment programs for preventing preterm delivery 2015 · Cochrane Headline outcomes only
  RR 0.55 [0.41, 0.75]
  1 study · 4155 participants
  Moderate

Intervention not reported

The intervention leads to lower preterm birth less than 34 weeks' gestation (high certainty).

• Home uterine monitoring for detecting preterm labour 2017 · Cochrane Headline outcomes only
  RR 0.78 [0.62, 0.99]
  3 studies · 1596 participants
  High

Intervention not reported

It is very uncertain whether the intervention changes preterm birth less than 37 weeks' gestation (very low certainty).

• Home uterine monitoring for detecting preterm labour 2017 · Cochrane Headline outcomes only
  RR 0.85 [0.72, 1.01]
  8 studies · 4834 participants
  Very low

SOF Immunological sealant vs usual care

It is very uncertain whether SOF Immunological sealant changes preterm birth less than 37 weeks' gestation compared with standard care (very low certainty).

• Sealing procedures for preterm prelabour rupture of membranes 2016 · Cochrane Headline outcomes only
  RR 0.48 [0.34, 0.68]
  1 study · 94 participants
  Very low

SOF Cervical adapter vs usual care

• Sealing procedures for preterm prelabour rupture of membranes 2016 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Vitamin D plus calcium vs placebo or no intervention

Vitamin D + calcium supplementation may leads to higher preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 1.52 [1.01, 2.28]
  5 studies · 942 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 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 vs placebo or no intervention

Vitamin D supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.66 [0.34, 1.3]
  7 studies · 1640 participants
  Low

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

Oral betamimetic vs placebo

Oral betamimetic showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo (low certainty).

• Prophylactic oral betamimetics for reducing preterm birth in women with a twin pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.85 [0.65, 1.1]
  4 studies · 276 participants
  Low

Oral betamimetic vs placebo

Oral betamimetic showed no clear difference in very preterm birth (less than 34 weeks' gestation) compared with placebo (low certainty).

• Prophylactic oral betamimetics for reducing preterm birth in women with a twin pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.47 [0.15, 1.5]
  1 study · 144 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 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