Vitamin D supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).
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).
Oral betamimetic showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo (low certainty).
It is very uncertain whether cervical cerclage in combination with antibiotics and tocolytics changes preterm birth < 34 completed weeks of pregnancy compared with cervical cerclage alone (very low certainty).
Lower genital tract infection screening probably leads to lower preterm low birthweight (below or equal 2500 g) compared with no screening (moderate certainty).
Antihelminthics showed no clear difference in preterm birth (birth before 37 weeks of gestation) compared with control (low certainty).
Oral betamimetic showed no clear difference in very preterm birth (less than 34 weeks' gestation) compared with placebo (low certainty).
Lower genital tract infection screening probably leads to lower preterm very low birthweight (below or equal 1500 g) compared with no screening (moderate certainty).
(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).
(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).
Setting of BP measurement: self‐measurement showed no clear difference in preterm birth (birth before 34 completed weeks' gestation) compared with conventional clinic measurement (low certainty).
The review found no eligible studies for this question.
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).
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).
The intervention showed no clear difference in very preterm birth (less than 34 weeks) ‐ assuming complete… (low certainty).
The intervention showed no clear difference in very preterm birth (less than 34 weeks) ‐ assuming complete… (low certainty).
The intervention leads to lower pregnancy with serious adverse outcome (composite including maternal… (high certainty).