Table 2 Meta-analysis results of factors influencing DOL
From: Incidence and factors influencing delayed onset of lactation: a systematic review and meta-analysis
Influencing factors | No. of studies | Heterogeneity test | Test model | Meta-analysis | Sensitivity analysis (Robust) | Egger’s test (t/p-value) | |||
|---|---|---|---|---|---|---|---|---|---|
p-value | I² (%) | Effect size | Value (95% CI) | p-value | |||||
Age | |||||||||
 Age (y) | 4 | 0.788 | 0.0 | F | WMD | -0.30 (-0.57, -0.04) | 0.022 | No | - |
 ≥ 35 y | 9 | 0.000 | 94.9 | R | RR | 1.40 (0.96, 2.04) | 0.081 | Yes | - |
 ≥ 30 y | 5 | 0.007 | 71.9 | R | RR | 1.33 (0.98, 1.80) | 0.064 | Yes | - |
Prepregnancy BMI | |||||||||
 ≥ 25.0 kg/m² | 8 | 0.001 | 71.9 | R | RR | 1.47 (1.17, 1.84) | 0.001 | Yes | - |
 ≥ 24.0 kg/m² | 3 | 0.228 | 32.4 | F | RR | 1.41 (1.14, 1.74) | 0.001 | Yes | - |
 BMI (kg/m²) | 3 | 0.000 | 96.6 | R | WMD | 1.26 (-1.22, 3.75) | 0.319 | Yes | - |
GWG (excessive)* | 7 | 0.000 | 81.5 | R | RR | 1.38 (1.07, 1.77) | 0.013 | No | - |
GDM | 14 | 0.010 | 53.0 | R | RR | 1.32 (1.18, 1.49) | 0.000 | Yes | 1.63/0.129 |
HDP | 13 | 0.000 | 82.1 | R | RR | 1.66 (1.30, 2.12) | 0.000 | Yes | -1.61/0.136 |
Thyroid disorders during pregnancy | 6 | 0.262 | 22.9 | F | RR | 1.18 (1.05, 1.32) | 0.005 | Yes | - |
Serum albumin level (g/L) < 35 | 2 | 0.294 | 9.3 | F | RR | 1.57 (1.12, 2.20) | 0.008 | - | - |
Primipara | 23 | 0.000 | 60.2 | R | RR | 1.40 (1.25, 1.56) | 0.000 | Yes | 1.60/0.125 |
Caesarean delivery | 20 | 0.000 | 77.0 | R | RR | 1.33 (1.17, 1.52) | 0.000 | Yes | 0.43/0.675 |
Unscheduled caesarean delivery | 2 | 0.749 | 0.0 | F | RR | 1.24(1.02, 1.51) | 0.033 | - | - |
Caesarean delivery history | 2 | 0.673 | 0.0 | F | RR | 0.75 (0.60, 0.93) | 0.009 | - | - |
Duration of labour (h) | 2 | 0.000 | 96.4 | R | WMD | 1.97 (-2.21, 6.16) | 0.356 | - | - |
Vaginal delivery, stage 2 labour duration > 1 h | 2 | 0.023 | 80.8 | R | RR | 1.41(0.73, 2.72) | 0.308 | - | - |
Sleep duration (h/d) | 2 | 0.585 | 0.0 | F | WMD | -0.24 (-0.45, -0.02) | 0.029 | - | - |
EPDS score ≥ 9 | 2 | 0.046 | 75.0 | R | RR | 1.24 (0.80, 1.93) | 0.340 | - | - |
Education level | Â | Â | Â | Â | Â | Â | Â | Â | Â |
 ≥ high school | 2 | 0.511 | 0.0 | F | RR | 1.04 (0.70, 1.55) | 0.848 | - | - |
 ≥ junior college | 3 | 0.098 | 56.9 | R | RR | 1.22 (0.84, 1.77) | 0.291 | Yes | - |
 ≥ undergraduate | 7 | 0.030 | 57.0 | R | RR | 1.07 (0.90, 1.27) | 0.472 | Yes | - |
 > 9 years | 2 | 0.069 | 69.8 | R | RR | 1.00 (0.62, 1.62) | 0.998 | - | - |
Occupational status (Yes) | 5 | 0.192 | 34.4 | F | RR | 0.99 (0.87, 1.14) | 0.927 | Yes | - |
Mean monthly household income | |||||||||
 ≤ 5,000 RMB/per person | 3 | 0.952 | 0.0 | F | RR | 1.13 (0.92, 1.37) | 0.238 | Yes | - |
 ≥ 10,000 RMB/per person | 3 | 0.365 | 0.9 | F | RR | 1.00 (0.91, 1.10) | 0.940 | Yes | - |
Nationality | |||||||||
 Hispanic | 3 | 0.268 | 24.1 | F | RR | 1.10 (0.94, 1.29) | 0.236 | Yes | - |
 White | 2 | 0.150 | 51.8 | R | RR | 0.97 (0.72, 1.30) | 0.841 | - | - |
 Han Chinese | 5 | 0.957 | 0.0 | F | RR | 0.90 (0.72, 1.13) | 0.352 | Yes | - |
Prenatal smoking status | 4 | 0.622 | 0.0 | F | RR | 1.02 (0.83, 1.24) | 0.872 | Yes | - |
Prenatal alcohol consumption status | 5 | 0.038 | 60.7 | R | RR | 1.41 (0.88, 2.26) | 0.157 | Yes | Â |
ART | 2 | 0.225 | 32.1 | F | RR | 1.10 (0.81, 1.49) | 0.547 | - | - |
Planned pregnancy | 2 | 0.000 | 97.8 | R | RR | 0.51 (0.11, 2.39) | 0.392 | - | - |
Insulin treatment | 2 | 0.483 | 0.0 | F | RR | 1.15 (0.71, 1.86) | 0.571 | - | - |
Fluid infusion (ml/d) | 2 | 0.211 | 36.0 | F | WMD | -21.31 (-72.93, 30.30) | 0.418 | - | - |
Gestational weeks | |||||||||
 <37 w | 7 | 0.019 | 60.4 | R | RR | 1.29 (1.06, 1.57) | 0.012 | Yes | - |
 Weeks (premature, w) | 2 | 0.726 | 0.0 | F | WMD | -0.47 (-0.89, -0.06) | 0.027 | - | - |
 ≥ 39 w | 2 | 0.656 | 0.0 | F | RR | 1.11 (0.86, 1.43) | 0.432 | - | - |
 Weeks (term, w) | 3 | 0.080 | 60.4 | R | WMD | -0.04(-0.26, 0.19) | 0.744 | Yes | - |
Birth weight | |||||||||
 <2.5 kg | 2 | 0.590 | 0.0 | F | RR | 1.34 (1.07, 1.67) | 0.011 | - | - |
 ≥ 4 kg | 3 | 0.271 | 23.5 | F | RR | 1.29 (1.07, 1.56) | 0.009 | No | - |
 Weight (kg) | 3 | 0.000 | 94.5 | R | WMD | -0.36 (-0.86, 0.14) | 0.160 | Yes | - |
 Premature infants (g) | 2 | 0.862 | 0.0 | F | WMD | -17.09 (-102.28, 68.09) | 0.694 | - | - |
Neonatal sex (male) | 9 | 0.897 | 0.0 | F | RR | 0.97 (0.89, 1.05) | 0.462 | Yes | - |
Apgar score | |||||||||
 < 7 (1 min) | 3 | 0.721 | 0.0 | F | RR | 1.29 (0.92, 1.81) | 0.141 | Yes | - |
 < 8 (1 min) | 3 | 0.018 | 75.1 | R | RR | 1.51 (0.78, 2.93) | 0.218 | Yes | - |
Breastfeeding guidance (Yes) | 7 | 0.116 | 41.3 | F | RR | 0.72 (0.64, 0.81) | 0.000 | Yes | - |
Breastfeeding information sources ≥ 3 | 2 | 0.000 | 95.0 | R | RR | 0.50 (0.15, 1.65) | 0.256 | - | - |
Breastfeeding frequency | |||||||||
 Frequency (t) | 5 | 0.000 | 84.7 | R | WMD | -0.63 (-1.10, -0.16) | 0.008 | Yes | - |
 Postoperative day 1 ≤ 2 t | 2 | 0.581 | 0.0 | F | RR | 1.92 (1.36, 2.72) | 0.000 | - | - |
 Postoperative day 2 ≤ 2 t | 2 | 0.583 | 0.0 | F | RR | 1.71 (1.34, 2.20) | 0.000 | - | - |
 Day 1 < 8 t | 2 | 0.904 | 0.0 | F | RR | 1.00 (0.78,1.28) | 0.970 | - | - |
History of breastfeeding | 3 | 0.007 | 79.6 | R | RR | 0.73 (0.46, 1.17) | 0.191 | Yes | - |
Previous insufficient lactation | 2 | 0.916 | 0.0 | F | RR | 0.89 (0.64, 1.24) | 0.491 | - | - |
Prenatal breast enlargement (No or a little) | 2 | 0.041 | 75.9 | R | RR | 1.35 (0.86, 2.11) | 0.192 | - | - |
Nipples (flat or sunken) | 4 | 0.009 | 74.2 | R | RR | 0.99 (0.62, 1.58) | 0.956 | Yes | - |
Bra cup size ≥ D | 2 | 0.080 | 67.3 | R | RR | 1.32 (0.74, 2.34) | 0.347 | - | - |