Table 2 Methodological quality of the studies included in the review.
| Study | Sample size estimate | Method of randomisation | Allocation Concealment | Blinding of intervention | Proportion (%) included in analysis* | Blinding of outcome | Baseline variables compared | Assessment of confounding |
|---|---|---|---|---|---|---|---|---|
| Davies9 | No | Randomised but method not stated | Not stated | Not stated | 100% | Not stated | Yes | Stratification by gestational age |
| Raiha et al10 | No | Blocked randomisation | Coding of bottles | Not stated | 95% | Not stated | Yes | Stratification by gestational age |
| Schultz et al11 | No | Randomised but method not stated | Not stated | Not stated | 100% | Not stated | Yes | No |
| Gross12 | No | Random number table | Not stated | Not stated | 100% | Not stated | Yes | No |
| Lucas et al13,14,15,16,17,18,19,20,21,22 | Yes | Blocked randomisation | Opaque, sealed, numbered envelopes | No | 100% for short term outcomes69% at 9 months 86% at 18 months 82% at 8 years | For some outcomes | Yes | For some outcomes |
| Cooper et al23 | No | Not random (alternating assignment) | Not stated | Not stated | 100% | Not stated | Yes | No |
| Putet et al24 | No | Not stated (may not be randomised) | Not stated | Not stated | 92% | Not stated | Yes | No |
*This is the percentage included in the analysis after excluding losses to follow‐up (for which there were very few for the short‐term outcomes) and those with missing values for some outcomes.