Table 3. Strength of evidence for the outcomes of interest.
| Outcome | Population; Comparator | NStudies | NSubjects | NEvents | Effect Estimate | SoE Domains* | SoE |
| Neonatal death† | Twins+RPTL; Oral tocolytics | 1 [19] | 706 | 12 | OR = 0.09 (0.01, 0.70) | Medium; N/A; Direct; Precise | Low |
| Singleton+RPTL; Oral nifedipine | 1 [17] | 284 | 0 | OR = 1.00 (0.02, 50.75) | Medium; N/A; Direct; Imprecise | Insufficient | |
| Significant IVH (Grade III/IV)† | Singleton+RPTL; No treatment | 1 [13] | 60 | 4 | OR = 0.30 (0.02, 5.85) | High; N/A; Direct; Imprecise | Insufficient |
| Incidence of delivery <32 weeks | Twins+RPTL; Oral nifedipine | 1 [16] | 656 | 192 | OR = 0.47 (0.33, 0.68) | Medium; N/A; Indirect; Precise | Low |
| Twins+RPTL; Oral tocolytics | 1 [19] | 706 | 124 | OR = 0.52 (0.35, 0.76) | Medium; N/A; Indirect; Precise | Low | |
| Singleton + RPTL; Oral nifedipine | 2 [15], [17] | 1650 | 106 | OR = 0.20–0.29 (0.07–0.16, 0.52–0.61)‡ | High/Medium; Consistent; Indirect; Precise | Low | |
| Singleton+RPTL; Oral tocolytics | 1 [18] | 558 | 37 | OR = 0.21 (0.09, 0.50) | High; N/A; Indirect; Precise | Low | |
| Singleton+RPTL; No treatment | 1 [13] | 60 | 21 | OR = 0.04 (0.00, 0.65) | High; N/A; Indirect; Precise | Low | |
| Incidence of delivery <37 weeks† | Singleton+RPTL; Oral nifedipine | 2 [15], [17] | 1650 | 925 | OR = 0.72–0.75 (0.47–0.58, 0.90–1.20)‡ | High/Medium; Consistent; Indirect; Imprecise | Insufficient |
| Singleton+RPTL; Oral tocolytics | 1 [18] | 558 | 318 | OR = 0.70 (0.50, 0.98) | High; N/A; Indirect; Precise | Low | |
| Singleton+RPTL; No treatment | 1 [13] | 60 | 50 | OR = 0.04 (0.01, 0.23) | High; N/A; Indirect; Precise | Low | |
| Singleton/Multiple+RPTL; Oral terbutaline | 1 [11] | 64 | 38 | OR = 0.10 (0.03, 0.32) | Medium; N/A; Indirect; Precise | Low | |
| Pregnancy prolongation (days)† | Twins+RPTL; Oral nifedipine | 1 [16] | 656 | N/A | MD = 7.20 (4.10, 10.30) | Medium; N/A; Indirect; Precise | Low |
| Singleton+RPTL; Oral nifedipine | 2 [15], [17] | 1650 | N/A | MD = 6.20–7.50 (0.79–4.94, 10.06–11.61)‡ | High/Medium; Consistent; Indirect; Imprecise | Insufficient | |
| Singleton+RPTL; Oral tocolytics | 1 [18] | 558 | N/A | MD = 5.50 (2.28, 8.72) | High; N/A; Indirect; Precise | Low | |
| Singleton+RPTL; No treatment | 1 [13] | 60 | N/A | MD = 25.30 (16.77, 33.83) | High; N/A; Indirect; Precise | Low |
Abbreviations: IVH = intraventricular hemorrhage; MD = mean difference; N = number; N/A = not applicable; OR = odds ratio; RPTL = recurrent preterm labor; SoE = strength of evidence.
*SoE domains are presented in the following order: Risk of Bias; Consistency; Directness; Precision.
RCT evidence was available for neonatal death [24], significant IVH [21], delivery <37 weeks [21], and pregnancy prolongation [21], [24]. There were no events of neonatal death or significant IVH. Nonsignificant differences were reported for incidence of delivery <37 weeks and pregnancy prolongation. The RCT evidence was not graded because it did not apply to any of the subgroups of interest.
These studies were not pooled. There was risk of double counting of participants across these studies.