Meta-regression analysis to identify possible factors of heterogeneity among the included studies
| Variables (reference category)* | Estimate | SE | Z value | P value | CI.lb | CI.ub |
| TIBF | ||||||
| ANC | ||||||
| Amhara region (Afar) | 1.71 | 1.17 | 1.46 | 0.15 | −0.59 | 4.01 |
| Oromia region (Afar) | 1.48 | 0.91 | 1.62 | 0.10 | −0.31 | 3.28 |
| SNNPR region (Afar) | 0.54 | 1.09 | 0.50 | 0.62 | −1.58 | 2.67 |
| Tigray region (Afar) | 1.58 | 1.30 | 1.21 | 0.23 | −0.97 | 4.12 |
| Urban residence (Rural) | 0.71 | 1.07 | 0.67 | 0.51 | −1.38 | 2.80 |
| Urban and rural residence (Rural) | 0.65 | 1.25 | 0.52 | 0.61 | −1.81 | 3.10 |
| ≥501 mothers (≤500 mothers) | −0.54 | 0.81 | −0.66 | 0.51 | −2.13 | 1.06 |
| Published 2016–2018 (2011–2015) | 0.14 | 0.82 | 0.17 | 0.87 | −1.47 | 1.74 |
| EBF | ||||||
| Gender of newborn | ||||||
| Oromia region (Amhara) | −0.54 | 0.24 | −2.22 | 0.03 | −1.02 | −0.06 |
| SNNPR region (Amhara) | 0.12 | 0.26 | 0.46 | 0.64 | −0.39 | 0.63 |
| Tigray region (Amhara) | −0.39 | 0.30 | −1.31 | 0.19 | −0.98 | 0.19 |
| Urban residence (Rural) | 0.79 | 0.51 | 1.57 | 0.12 | −0.20 | 1.78 |
| Urban and rural residence (Rural) | −0.10 | 0.44 | −0.24 | 0.81 | −0.96 | 0.75 |
| ≥501 mothers (≤500 mothers) | 0.78 | 0.23 | 3.34 | <0.001 | 0.32 | 1.24 |
| Published 2016–2018 (2011–2015) | −1.14 | 0.44 | −2.59 | 0.01 | −1.99 | −0.28 |
| ANC | ||||||
| Harari region (Amhara) | −0.11 | 0.64 | −0.17 | 0.87 | −1.37 | 1.16 |
| Oromia region (Amhara) | −1.27 | 0.39 | −3.28 | 0.001 | −2.03 | −0.51 |
| SNNPR region (Amhara) | 0.09 | 0.35 | 0.27 | 0.78 | −0.59 | 0.78 |
| Tigray region (Amhara) | −0.49 | 0.57 | −0.87 | 0.38 | −1.60 | 0.62 |
| Urban residence (Rural) | −0.18 | 0.38 | −0.47 | 0.63 | −0.92 | 0.56 |
| Urban and rural residence (Rural) | −0.26 | 0.52 | −0.49 | 0.62 | −1.28 | 0.76 |
| ≥501 mothers (≤500 mothers) | −0.30 | 0.34 | −0.87 | 0.38 | −0.96 | 0.37 |
| Published 2016–2018 (2011–2015) | 0.08 | 0.28 | 0.29 | 0.77 | −0.46 | 0.62 |
| PNC† | ||||||
| Harari region (Amhara) | −0.60 | 0.48 | −1.24 | 0.22 | −1.54 | 0.35 |
| SNNPR region (Amhara) | 0.25 | 0.30 | 0.82 | 0.41 | −0.34 | 0.83 |
| Tigray region (Amhara) | −0.16 | 0.64 | −0.25 | 0.80 | −1.42 | 1.10 |
| ≥501 mothers (≤500 mothers) | 0.11 | 0.31 | 0.36 | 0.72 | −0.50 | 0.73 |
| Published 2016–2018 (2011–2015) | 0.26 | 0.36 | 0.71 | 0.47 | −0.45 | 0.96 |
*Since we do not have a specific hypothesis, the reference category is selected arbitrarily; †Residence is dropped from the model due to small sample size of included studies. Cut-off value for sample size and publication year was arbitrarily chosen.
ANC, antenatal care; CI.lb, CI interval, lower bound; CI.ub, CI interval, upper bound; EBF, exclusive breast feeding; PNC, postnatal care; SNNPR, Southern Nations, Nationalities and Peoples’ Region; TIBF, timely initiation of breast feeding.