Interventions During Pregnancy to Prevent Preterm Birth: an Overview of Cochrane…

Medley N, Vogel JP, Care A, Alfirevic Z. Interventions during pregnancy to prevent preterm birth: an overview of Cochrane systematic reviews. Cochrane Database Syst Rev. 2018 Nov 14;11(11):CD012505. doi: 10.1002/14651858.CD012505.pub2. PMID: 30480756; PMCID: PMC6516886.

Background
Preterm birth (PTB) is a major factor contributing to global rates of neonatal death and to longer-term health problems for surviving infants. Both the World Health Organization and the United Nations consider prevention of PTB as central to improving health care for pregnant women and newborn babies. Current preventative clinical strategies show varied efficacy in different populations of pregnant women, frustrating women and health providers alike, while researchers call for better understanding of the underlying mechanisms that lead to PTB.

Methods
We searched the Cochrane Database of Systematic Reviews (2 November 2017) with key words to capture any Cochrane SR that prespecified or reported a PTB outcome. Inclusion criteria focused on pregnant women without signs of preterm labour or ruptured amniotic membranes. We included reviews of interventions for pregnant women irrespective of their risk status. We followed standard Cochrane methods.We applied GRADE criteria to evaluate the quality of SR evidence. We assigned graphic icons to classify the effectiveness of interventions as: clear evidence of benefit; clear evidence of harm; clear evidence of no effect or equivalence; possible benefit; possible harm; or unknown benefit or harm. We defined clear evidence of benefit and clear evidence of harm to be GRADE moderate- or high-quality evidence with a confidence interval (CI) that does not cross the line of no effect. Clear evidence of no effect or equivalence is GRADE moderate- or high-quality evidence with a narrow CI crossing the line of no effect. Possible benefit and possible harm refer to GRADE low-quality evidence with a clear effect (CI does not cross the line of no effect) or GRADE moderate- or high-quality evidence with a wide CI. Unknown harm or benefit refers to GRADE low- or very low-quality evidence with a wide CI.

Authors’ conclusions
Implications for practiceThe overview serves as a map and guide to all current evidence relevant to PTB prevention published in the Cochrane Library. Of 70 SRs with outcome data, we identified 36 reviews of interventions with the aim of preventing PTB. Just four of these SRs had evidence of clear benefit to women, with an additional four SRs reporting possible benefit. No SR reported clear harm, which is an important finding for women and health providers alike.The overview summarises no evidence for the clinically important interventions of cervical pessary, cervical length assessment and vaginal progesterone because these Cochrane Reviews were not current. These are active areas for PTB research.The graphic icons we assigned to SR effect estimates do not constitute clinical guidance or an endorsement of specific interventions for pregnant women. It remains critical for pregnant women and their healthcare providers to carefully consider whether specific strategies to prevent PTB will be of benefit for individual women, or for specific populations of women.Implications for researchFormal consensus work is needed to establish standard language for overviews of reviews and to define the limits of their interpretation.Clinicians, researchers and funders must address the lack of evidence for interventions relevant to women at high risk of PTB due to multiple pregnancy.

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