Table 1.
Study characteristics.
| Characteristic | N | % |
|---|---|---|
| Study design | ||
| Prospective cohort | 38 | 53.6 |
| Retrospective cohort | 16 | 22.5 |
| Case-control | 17 | 23.9 |
| Location of data collection | ||
| Hospital | 58 | 81.7 |
| Primary health units | 7 | 9.9 |
| Community | 3 | 8.4 |
| Differential diagnosis of exposure | ||
| Maternal anemia | 65 | 91.6 |
| Iron deficiency anemia | 6 | 8.4 |
| Hemoglobin levels * | ||
| <11 g/dL | 54 | 77.1 |
| <10 g/dL | 10 | 14.3 |
| <8 g/dL | 6 | 8.6 |
| Geographic region | ||
| America | 9 | 12.7 |
| Africa | 6 | 8.4 |
| Asia | 44 | 62.0 |
| Europe | 8 | 11.3 |
| Oceania | 4 | 5.6 |
| Sample size | ||
| ≤1000 | 43 | 60.6 |
| >1000 | 28 | 39.4 |
| Methodological quality of the studies | ||
| Moderate | 40 | 56.3 |
| High | 31 | 43.7 |
| Year the research was initiated ** | ||
| Before 1990 | 8 | 14.0 |
| 1990–2009 | 12 | 21.0 |
| 2000–2009 | 25 | 44.0 |
| 2010–2017 | 12 | 21.0 |
| Control for confounding | ||
| Yes | 20 | 28.2 |
| No | 51 | 71.8 |
* One study did not present the definition but affirmed that there was a reduction in birth weight. ** Some studies did not report the start date of the survey.