Appendix 1.
Quality review criteria for included studies based on the Newcastle-Ottawa Quality Assessment Scale for cohort studies
| Quality assessment items | Score |
|---|---|
| Selection (maximum score = 4) | |
| Representativeness of the exposed cohort | |
| Truly or somewhat representative of the average child in the community | 1 |
| Selected group of users or no description of the derivation of the cohort | 0 |
| Selection of the non-exposed cohort | |
| Drawn from the same community as the exposed cohort | 1 |
| Drawn from a different source or no description | 0 |
| Ascertainment of exposure | |
| Secure record, structured interview or administered questionnaire | 1 |
| Written self-report questionnaire or no description | 0 |
| Demonstration that the outcome was not present at the start of the study | |
| Yes | 1 |
| No | 0 |
| Comparability (maximum score = 2) | |
| Comparability of the cohorts on the basis of the design or analysis | |
| Study controls for essential confounding variables (SES indicator and maternal BMI) and additional relevant confounders | 2 |
| Study controls for some relevant confounding variables | 1 |
| Inadequate consideration of confounding variables | 0 |
| Outcome (maximum score = 3) | |
| Assessment of outcome | |
| Objective measurement of height and weight | 1 |
| Self-report or no description | 0 |
| Was follow-up long enough for outcomes to occur | |
| Yes | 1 |
| No | 0 |
| Adequacy of follow-up | |
| Complete follow-up or subjects lost to follow-up unlikely to introduce bias (small number lost or description provided of lost) | 1 |
| Inadequate follow-up rate or no description provided of those lost | 0 |