Table 1. Interventions meeting selection criteria for analysis of prevention of preterm birth.

Interventions	Evidence of efficacy for preterm birth by GRADE criteria	Rec. for implementation for preterm birth	Rationale for inclusion / exclusion in analysis
Smoking cessation	High	Strong	Included: GRADE recommendation according to GAPPS
Progesterone	High	Strong	Included : GRADE recommendation according to GAPPS
Cerclage	High no effect	Strong against	Included: newer evidence16 shows efficacy in women with prior preterm birth and short cervix. Potential for implementation expected to be high among HIC, unlike that for L- and MIC, which was focus of GAPPS
Decrease non-medically indicated Caesarean delivery and induction	n/a	n/a	Included: relevant in HIC. (Not included in15 GAPPS given focus on L- and MIC)
Limit multiple embryo transfer in assisted reproductive technology	n/a	n/a	Included: relevant in HIC. (Not included in15 given focus on L- and MIC)
Zinc supplementation	High	Weak	Excluded: weak GRADE recommendation according to GAPPS

Notes: GAPPS Global Alliance for Prevention of Prematurity and Stillbirth, report.¹⁵ New evidence supporting efficacy of cerclage from Berghella et al Obstetrics and Gynecology 2011.¹⁶

GRADE = Grading of Recommendations Assessment, Development and Evaluation.

H-, M-, LIC are high-, middle-, and low-income countries. See webappendix p.18-19 for effect estimate applied for each intervention and webappendix p. 17 for other intervention that were considered but excluded from analysis.