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Search review questions
Each row is one question a systematic review asked: who, what, compared with what, and which outcome, with the effect it found and how certain that is. Words match anywhere in the field.
103 questions in 57 reviews
current versionsNo studies 4 · 3.9%Ungraded 9 · 8.7%Very low 19 · 18.4%Low 37 · 35.9%Moderate 20 · 19.4%High 14 · 13.6%
Ungraded means an effect was reported without a GRADE rating; it is not a gap. No studies means the review found nothing to answer the question. The six categories are a display order, not a score.
| Question | Effect | Evidence | Status / GRADE |
|---|---|---|---|
Summary of findings table ‐ Midwife continuity of care models vs other models of care Preterm birth (< 37 weeks) · childbearing women and their infants (all) (critical outcomes) Midwife continuity of care models versus other models of care for childbearing women (2024) · Cochrane | RR 0.95 [0.78, 1.16] | 10 studies · 13850 participants | Low |
Summary of findings table ‐ Vitamin B12 supplementation vs placebo/no vitamin B12 supplementation Preterm birth (< 37 weeks) · pregnant women Vitamin B12 supplementation during pregnancy for maternal and child health outcomes (2024) · Cochrane | RR 0.97 [0.55, 1.74] | 2 studies · 340 participants | Low |
Respiratory syncytial virus vaccine vs placebo Preterm birth · pregnant woman Respiratory syncytial virus vaccination during pregnancy for improving infant outcomes (2024) · Cochrane | RR 1.16 [0.99, 1.36] | 6 studies · 17560 participants | Very low |
Zinc supplementation vs no zinc (with or without placebo) Preterm birth (< 37 weeks) · Pregnant women (healthy and probable zinc deficiency) Zinc supplementation for improving pregnancy and infant outcome (2021) · Cochrane | RR 0.87 [0.74, 1.03] | 21 studies · 9851 participants | Low |
Antihelminthics vs control Preterm birth (birth before 37 weeks of gestation) · pregnant women in second trimester of pregnancy Effect of mass deworming with antihelminthics for soil‐transmitted helminths during pregnancy (2021) · Cochrane | RR 0.84 [0.38, 1.86] | 1 study · 1042 participants | Low |
Setting of BP measurement: self‐measurement vs conventional clinic measurement Preterm birth (birth before 34 completed weeks' gestation) · pregnant women with chronic or gestational hypertension Setting and techniques for monitoring blood pressure during pregnancy (2020) · Cochrane | RR 1.15 [0.37, 3.55] | 1 study · 154 participants | Low |
Technique of BP measurement: Korotkoff phase IV vs Korotkoff phase V to represent diastolic BP Preterm birth · pregnant women with diastolic hypertension Setting and techniques for monitoring blood pressure during pregnancy (2020) · Cochrane | no estimate extracted | NR | No studies |
Technique of BP measurement: CRADLE intervention vs usual care Preterm birth · pregnant women, or those within 42 days of delivery Setting and techniques for monitoring blood pressure during pregnancy (2020) · Cochrane | no estimate extracted | NR | No studies |
Cervical cerclage in combination with antibiotics and tocolytics vs cervical cerclage alone Preterm birth < 34 completed weeks of pregnancy Cervical stitch (cerclage) in combination with other treatments for preventing spontaneous preterm birth in… (2020) · Cochrane | RR 0.78 [0.44, 1.4] | 1 study · 50 participants | Very low |
GM‐CSF‐supplemented culture media vs culture media not supplemented with GM‐CSF Preterm birth · women undergoing assisted reproduction GM‐CSF (granulocyte macrophage colony‐stimulating factor) supplementation in culture media for women… (2020) · Cochrane | OR 1.2 [0.7, 2.04] | 2 studies · 1432 participants | Very low |
Antibiotics vs no treatment Preterm birth < 37 weeks · pregnant women with asymptomatic bacteriuria Antibiotics for asymptomatic bacteriuria in pregnancy (2019) · Cochrane | RR 0.34 [0.13, 0.88] | 3 studies · 327 participants | Low |
Progestogen vs placebo/no treatment Preterm birth · women with recurrent miscarriage of unclear etiology Progestogen for preventing miscarriage in women with recurrent miscarriage of unclear etiology (2019) · Cochrane | RR 1.13 [0.53, 2.41] | 4 studies · 256 participants | Very low |
Intervention NR Preterm birth (before 37 weeks' gestation) · pregnant women considered to be at risk of developing pre‐eclampsia Antiplatelet agents for preventing pre‐eclampsia and its complications (2019) · Cochrane | RR 0.91 [0.87, 0.95] | 47 studies · 35212 participants | High |
Intervention NR Pregnancy with serious adverse outcome (composite including maternal death, baby death, pre‐eclampsia, small‐for‐gestational age, preterm birth) ‐ only trials with individual participant data · pregnant women considered to be at risk of developing pre‐eclampsia Antiplatelet agents for preventing pre‐eclampsia and its complications (2019) · Cochrane | RR 0.9 [0.85, 0.96] | 13 studies · 17382 participants | High |
Multiple micronutrients vs control (iron with or without folic acid) Preterm births · women during pregnancy Multiple‐micronutrient supplementation for women during pregnancy (2019) · Cochrane | RR 0.95 [0.9, 1.01] | 18 studies · 91425 participants | Moderate |
Main comparison (FFN knowledge vs no knowledge) Preterm birth < 37 weeks · women with singleton pregnancies and threatened preterm labor (PTL) between 23 to 35 weeks Fetal fibronectin testing for reducing the risk of preterm birth (2019) · Cochrane | RR 0.72 [0.52, 1.01] | 5 studies · 434 participants | Low |
Main comparison (FFN knowledge vs no knowledge) Preterm birth < 34 weeks · women with singleton pregnancies and threatened preterm labor (PTL) between 23 to 35 weeks Fetal fibronectin testing for reducing the risk of preterm birth (2019) · Cochrane | RR 1.09 [0.54, 2.18] | 4 studies · 357 participants | Low |
Main comparison (FFN knowledge vs no knowledge) Preterm birth < 32 weeks · women with singleton pregnancies and threatened preterm labor (PTL) between 23 to 35 weeks Fetal fibronectin testing for reducing the risk of preterm birth (2019) · Cochrane | RR 0.79 [0.16, 3.96] | 4 studies · 357 participants | Very low |
Intervention NR Preterm birth < 34 weeks · women carrying twins, asymptomatic for PTL or PPROM Cervical assessment by ultrasound for preventing preterm delivery (2019) · Cochrane | RR 0.62 [0.3, 1.25] | 1 study · 125 participants | Very low |
Intervention NR Preterm birth < 37 weeks · singleton pregnancy with symptoms of PTL Cervical assessment by ultrasound for preventing preterm delivery (2019) · Cochrane | RR 0.59 [0.26, 1.32] | 2 studies · 242 participants | Very low |
Vitamin D + calcium supplementation vs placebo or no intervention Preterm birth (less than 37 weeks' gestation) · pregnant women and their infants.. Vitamin D supplementation for women during pregnancy (2019) · Cochrane | 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) Preterm birth (less than 37 weeks' gestation) · pregnant women and their infants.. Vitamin D supplementation for women during pregnancy (2019) · Cochrane | RR 1.04 [0.68, 1.59] | 1 study · 1298 participants | Low |
Vitamin D supplementation vs placebo or no intervention Preterm birth (less than 37 weeks' gestation) · pregnant women and their infants. Vitamin D supplementation for women during pregnancy (2019) · Cochrane | RR 0.66 [0.34, 1.3] | 7 studies · 1640 participants | Low |
Vaginal progesterone vs no treatment or placebo Preterm birth less than 37 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 0.97 [0.89, 1.06] | 6 studies · 1597 participants | Moderate |
Vaginal progesterone vs no treatment or placebo Preterm birth less than 28 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 1.53 [0.79, 2.97] | 3 studies · 1345 participants | Low |
Intramuscular (IM) progesterone vs no treatment or placebo Preterm birth less than 34 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 1.54 [1.06, 2.26] | 2 studies · 399 participants | Low |
Intramuscular (IM) progesterone vs no treatment or placebo Preterm birth less than 28 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 1.08 [0.75, 1.55] | 5 studies · 1920 participants | Moderate |
Intramuscular (IM) progesterone vs no treatment or placebo Preterm birth less than 37 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 1.05 [0.98, 1.13] | 5 studies · 2010 participants | High |
Vaginal progesterone vs no treatment or placebo Preterm birth less than 34 weeks · Women with a multiple pregnancy Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple… (2019) · Cochrane | RR 0.9 [0.66, 1.23] | 5 studies · 1503 participants | Low |
A dose of vitamin D 601 IU or higher vs 600 IU or lower alone or with other nutrients Preterm birth · women during pregnancy. Regimens of vitamin D supplementation for women during pregnancy (2019) · Cochrane | RR 1.25 [0.92, 1.69] | 4 studies · 2294 participants | Low |
A dose of vitamin D 4000 IU/d or more vs 3999 IU/d or less alone or with any other nutrient Preterm birth · women during pregnancy Regimens of vitamin D supplementation for women during pregnancy (2019) · Cochrane | RR 0.85 [0.64, 1.12] | 6 studies · 2948 participants | Low |
Dental caries during pregnancy vs Pregnant women without dental caries Preterm birth stratified by clinical type (spontaneous vs iatrogenic vs term) · Pregnant women · By type of PTB (spontaneous vs iatrogenic) Dental caries and preterm birth: a systematic review and meta-analysis. (2018) | no estimate extracted | 0 studies | Ungraded |
Dental caries during pregnancy vs Pregnant women without dental caries Preterm birth stratified by gestational age at birth (moderate-to-late 32 to <37, very 28 to <32, extremely <28 weeks) · Pregnant women · By gestational age at birth Dental caries and preterm birth: a systematic review and meta-analysis. (2018) | no estimate extracted | 0 studies | Ungraded |
Dental caries during pregnancy vs Pregnant women without dental caries Preterm birth (<37 weeks of gestation) · Pregnant women Dental caries and preterm birth: a systematic review and meta-analysis. (2018) | OR 1.16 [0.90, 1.49] | 5 studies · 4246 participants | Ungraded |
Intervention NR Preterm birth · pregnant women Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems (2018) · Cochrane | RR 0.76 [0.6, 0.97] | 11 studies · 15275 participants | Low |
Any antihypertensive drug vs no antihypertensive drugs/placebo Preterm birth (< 37 weeks) · women with mild to moderate hypertension during pregnancy Antihypertensive drug therapy for mild to moderate hypertension during pregnancy (2018) · Cochrane | RR 0.96 [0.83, 1.12] | 15 studies · 2141 participants | Moderate |
Intervention NR Preterm birth < 37 weeks · pregnant women and their babies Omega‐3 fatty acid addition during pregnancy (2018) · Cochrane | RR 0.89 [0.81, 0.97] | 26 studies · 10304 participants | High |
Intervention NR Early preterm birth < 34 weeks · pregnant women and their babies Omega‐3 fatty acid addition during pregnancy (2018) · Cochrane | RR 0.58 [0.44, 0.77] | 9 studies · 5204 participants | High |
Progesterone vs placebo or no treatment Preterm birth · women with threatened miscarriage Progestogen for treating threatened miscarriage (2018) · Cochrane | RR 0.86 [0.52, 1.44] | 5 studies · 588 participants | Low |
Intervention NR Any preterm birth (birth < 37 weeks) · women with a previous stillbirth of > 20 weeks' gestation who are pregnant or considering a subsequent pregnancy Care prior to and during subsequent pregnancies following stillbirth for improving outcomes (2018) · Cochrane | RR 0.42 [0.04, 4.06] | 1 study · 24 participants | Very low |
Intervention NR Any preterm birth (birth < 37 weeks) · women with a previous stillbirth of ≥ 20 weeks' gestation who are pregnant or considering a subsequent pregnancy Care prior to and during subsequent pregnancies following stillbirth for improving outcomes (2018) · Cochrane | RR 1.01 [0.58, 1.74] | 3 studies · 114 participants | Low |
Probiotics administered to pregnant women at risk of preterm birth vs placebo or no intervention Preterm birth < 37 weeks' gestation · prevention of morbidity and mortality in preterm infants Maternal probiotic supplementation for prevention of morbidity and mortality in preterm infants (2018) · Cochrane | RR 0.92 [0.32, 2.67] | 4 studies · 518 participants | Low |
Probiotics administered to pregnant women at risk of preterm birth vs placebo or no intervention Preterm birth < 34 weeks' gestation · prevention of morbidity and mortality in preterm infants Maternal probiotic supplementation for prevention of morbidity and mortality in preterm infants (2018) · Cochrane | no estimate extracted | 2 studies · 287 participants | Very low |
Summary of findings: lipid‐based nutrient supplements (LNS) vs multiple micronutrients (MMN) Preterm births (births before 37 weeks of gestation) · pregnant women Lipid‐based nutrient supplements for maternal, birth, and infant developmental outcomes (2018) · Cochrane | RR 1.15 [0.93, 1.42] | 3 studies · 2393 participants | Moderate |
Summary of findings: lipid‐based nutrient supplements (LNS) vs iron folic acid (IFA) Preterm births (births before 37 weeks of gestation) · pregnant women Lipid‐based nutrient supplements for maternal, birth, and infant developmental outcomes (2018) · Cochrane | RR 0.94 [0.8, 1.11] | 3 studies · 5924 participants | Moderate |
Periodontal treatment (scaling and root planing, polishing, or surgery), alone or with oral hygiene counselling, antiseptics, or antimicrobials vs No treatment Gestational age (preterm birth < 37 weeks) · Pregnant women considered to have periodontal disease (gingivitis or periodontitis) after dental examination Treating periodontal disease for preventing adverse birth outcomes in pregnant women (2017) · Cochrane | RR 0.87 [0.70, 1.10] | 11 studies · 5671 participants | Low |
Periodontal treatment (scaling and root planing, polishing, or surgery), alone or with oral hygiene counselling, antiseptics, or antimicrobials vs No treatment Preterm birth < 35 weeks · Pregnant women considered to have periodontal disease (gingivitis or periodontitis) after dental examination Treating periodontal disease for preventing adverse birth outcomes in pregnant women (2017) · Cochrane | RR 1.19 [0.81, 1.76] | 2 studies · 2557 participants | Very low |
Periodontal treatment (scaling and root planing, alone or with antimicrobials) vs Alternative (less intensive) periodontal treatment, alone or with placebo Gestational age (preterm birth < 37 weeks) · Pregnant women considered to have periodontal disease (gingivitis or periodontitis) after dental examination · SRP + antimicrobial vs alternative mechanical treatment + placebo Treating periodontal disease for preventing adverse birth outcomes in pregnant women (2017) · Cochrane | RR 1.40 [0.67, 2.92] | 1 study · 243 participants | Very low |
Periodontal treatment (scaling and root planing, polishing, or surgery), alone or with oral hygiene counselling, antiseptics, or antimicrobials vs No treatment Preterm birth < 32 weeks · Pregnant women considered to have periodontal disease (gingivitis or periodontitis) after dental examination Treating periodontal disease for preventing adverse birth outcomes in pregnant women (2017) · Cochrane | RR 1.35 [0.78, 2.32] | 3 studies · 2755 participants | Very low |
Periodontal treatment (scaling and root planing, alone or with antimicrobials) vs Alternative (less intensive) periodontal treatment, alone or with placebo Gestational age (preterm birth < 37 weeks) · Pregnant women considered to have periodontal disease (gingivitis or periodontitis) after dental examination · SRP vs alternative mechanical treatment Treating periodontal disease for preventing adverse birth outcomes in pregnant women (2017) · Cochrane | RR 0.87 [0.46, 1.67] | 4 studies · 1168 participants | Very low |