Comparison 1. Exclusive breastfeeding for 6 versus 4 months, developing countries, controlled trials.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Monthly weight gain from 4‐6 months (g/mo)	2	265	Mean Difference (IV, Fixed, 95% CI)	20.78 [‐21.99, 63.54]
2 Monthly weight gain from 6‐12 months (g/mo)	2	233	Mean Difference (IV, Fixed, 95% CI)	‐2.62 [‐25.85, 20.62]
3 Monthly length gain 4‐6 months (cm/mo)	2	265	Mean Difference (IV, Fixed, 95% CI)	0.10 [‐0.04, 0.24]
4 Monthly length gain 6‐12 months (cm/mo)	2	233	Mean Difference (IV, Fixed, 95% CI)	‐0.04 [‐0.10, 0.02]
5 Weight‐for‐age z‐score at 6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	0.18 [‐0.06, 0.41]
6 Length‐for‐age z‐score at 6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	0.11 [‐0.11, 0.33]
7 Weight‐for‐length z‐score at 6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	0.09 [‐0.13, 0.31]
8 Weight‐for‐age z‐score < ‐2 at 6 months	2	260	Risk Ratio (M‐H, Fixed, 95% CI)	2.14 [0.74, 6.24]
9 Length‐for‐age z‐score < ‐2 at 6 months	2	260	Risk Ratio (M‐H, Fixed, 95% CI)	1.18 [0.56, 2.50]
10 Weight‐for‐length z‐score < ‐2 at 6 months	2	260	Risk Ratio (M‐H, Fixed, 95% CI)	1.38 [0.17, 10.98]
11 Receipt of Fe supplements 6‐9 months	1	139	Risk Ratio (M‐H, Fixed, 95% CI)	1.20 [0.91, 1.58]
12 Hemoglobin concentration (g/L) at 6 months	1	139	Mean Difference (IV, Fixed, 95% CI)	‐5.0 [‐8.46, ‐1.54]
13 Hemoglobin concentration < 110 g/L at 6 months	1	139	Risk Ratio (M‐H, Fixed, 95% CI)	1.20 [0.91, 1.58]
14 Hemoglobin concentration < 103 g/L at 6 months	1	139	Risk Ratio (M‐H, Fixed, 95% CI)	1.29 [0.75, 2.23]
15 Hematocrit (%) at 6 months	1	139	Mean Difference (IV, Fixed, 95% CI)	‐1.20 [‐2.15, ‐0.25]
16 Hematocrit < 33% at 6 months	1	139	Risk Ratio (M‐H, Fixed, 95% CI)	1.50 [0.85, 2.64]
17 Plasma ferritin concentration (mcg/L) at 6 months	1	135	Mean Difference (IV, Fixed, 95% CI)	‐18.9 [‐37.31, ‐0.49]
18 Plasma ferritin concentration < 12 mcg/L at 6 months	1	135	Risk Ratio (M‐H, Fixed, 95% CI)	2.34 [0.86, 6.35]
19 Plasma ferritin concentration < 15 mcg/L at 6 months	1	135	Risk Ratio (M‐H, Fixed, 95% CI)	2.93 [1.13, 7.56]
20 Plasma zinc concentration < 70 mcg/dL at 6 months	1	101	Risk Ratio (M‐H, Fixed, 95% CI)	0.75 [0.43, 1.33]
21 % of days with fever 4‐6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	0.26 [‐1.29, 1.81]
22 % of days with cough 4‐6 months	2	260	Mean Difference (IV, Random, 95% CI)	2.33 [‐6.00, 12.65]
23 % of days with nasal congestion 4‐6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	0.11 [‐4.41, 4.63]
24 % of days with nasal discharge 4‐6 months	2	260	Mean Difference (IV, Random, 95% CI)	‐0.72 [‐6.81, 5.38]
25 % of days with hoarseness 4‐6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	‐0.19 [‐1.17, 0.79]
26 % of days with diarrhea 4‐6 months	2	260	Mean Difference (IV, Fixed, 95% CI)	1.15 [‐0.35, 2.65]
27 % of days with fever 6‐12 months	2	258	Mean Difference (IV, Fixed, 95% CI)	‐0.39 [‐2.80, 2.02]
28 % of days with nasal congestion 6‐12 months	2	258	Mean Difference (IV, Fixed, 95% CI)	3.11 [‐0.12, 6.35]
29 % of days with diarrhea 6‐12 months	2	258	Mean Difference (IV, Fixed, 95% CI)	‐0.74 [‐2.34, 0.86]
30 Age first crawled (mo)	2	240	Mean Difference (IV, Fixed, 95% CI)	‐0.80 [‐1.26, ‐0.34]
31 Age first sat from lying position (mo)	2	238	Mean Difference (IV, Random, 95% CI)	‐0.22 [‐0.91, 0.46]
32 Did not walk by 12 months	2	233	Risk Ratio (M‐H, Random, 95% CI)	0.88 [0.50, 1.55]
33 Maternal postpartum weight loss 4‐6 months (kg)	2	260	Mean Difference (IV, Fixed, 95% CI)	0.42 [0.02, 0.82]
34 Maternal resumption of menses 6 months postpartum	2	189	Risk Ratio (M‐H, Fixed, 95% CI)	0.58 [0.33, 1.03]