Table 3 Subgroup analysis for the evaluation the effect of following variables in the development of significant heterogeneity in the meta-analysis
Subgroup | Number of studies | SMD (95% CI) | P-value | Test of heterogeneity | |
|---|---|---|---|---|---|
I2% | P-value | ||||
Overall results | 13 | 1.84 (0.47, 3.21) | 0.008 | 98.06 | 0 |
Maternal age (year) | |||||
< 30 | 9 | 2.87 (0.68, 5.05) | 0.01 | 98.05 | 0 |
≥ 30 | 4 | -0.21 (-2.27,1.84) | 0.83 | 97.7 | 0 |
Gestational age at delivery (week) | |||||
≤ 36 | 6 | 1.35 (-0.60, 3.3) | 0.17 | 96.9 | 0 |
> 36 | 6 | 2.98 (0.58, 5.3) | 0.015 | 97.7 | 0 |
Birth weight (g) | |||||
< 2500 | 2 | 4.68 (-0.06, 9.4) | 0.05 | 92.1 | 0 |
> 2500 | 6 | 2.53 (0.71, 4.3) | 0.006 | 96.7 | 0 |
Sample | |||||
Placenta | 9 | 1.81 (-0.85, 4.4) | 0.18 | 98.4 | 0 |
Body fluids (serum, plasma) | 4 | 2.16 (0.84, 3.49) | 0.001 | 96.6 | 0 |
Proteinuria (mg/24h) | |||||
≤ 300 | 2 | 6.02 (-1.6, 13.6) | 0.12 | 98.1 | 0 |
> 300 | 5 | -0.56 (-4.2, 3.1) | 0.76 | 98.5 | 0 |