Association between any or exclusive BF and developmental delay for the full sample (n=77 119)
| Developmental delay at 6 months | Developmental delay at 12 months | |||||
| No | cRR(95% CI) | aRR (95% CI)*† | No | cRR (95% CI) | aRR (95% CI)*† | |
| (A) Any BF | ||||||
| Until 6 months | ||||||
| No | 1263/12 967 (9.7%) | 1 (reference) | 1 (reference) | 2091/12 735 (16.4%) | 1 (reference) | 1 (reference) |
| Yes | 4899/60 383 (8.1%) | 0.83 (0.79 to 0.88) | 0.81 (0.76 to 0.86) | 8351/59 003 (14.2%) | 0.86 (0.82 to 0.90) | 0.81 (0.77 to 0.85) |
| Until 12 months | ||||||
| No | — | — | — | 4061/25 303 (16.0%) | 1 (reference) | 1 (reference) |
| Yes | — | — | — | 6381/46 435 (13.7%) | 0.86 (0.83 to 0.89) | 0.81 (0.78 to 0.84) |
| Developmental delay at 6 months | Developmental delay at 12 months | |||||
| No | cRR(95% CI) | aRR(95% CI)* | No | cRR (95% CI) | aRR (95% CI)* | |
| (B) Exclusive BF | ||||||
| Until 3 months | ||||||
| No | 3794/43 558 (8.7%) | 1 (reference) | 1 (reference) | 6637/42 648 (15.6%) | 1 (reference) | 1 (reference) |
| Yes | 2273/28 685 (7.9%) | 0.91 (0.87 to 0.96) | 0.95 (0.90 to 1.00) | 3664/28 050 (13.1%) | 0.84 (0.81 to 0.87) | 0.86 (0.83 to 0.90) |
| Until 6 months | ||||||
| No | 4768/57 508 (8.3%) | 1 (reference) | 1 (reference) | 8228/56 374 (14.6%) | 1 (reference) | 1 (reference) |
| Yes | 1299/14 735 (8.8%) | 1.06 (1.00 to 1.13) | 1.04 (0.98 to 1.11) | 2073/14 324 (14.5%) | 0.99 (0.95 to 1.04) | 0.97 (0.92 to 1.01) |
| Developmental delay at 6 months | Developmental delay at 12 months | |||||
| No | cRR (95% CI) | aRR (95% CI)* | No | cRR (95% CI) | aRR (95% CI)* | |
| (C) BF until 6 months | ||||||
| FF(−), CF(−) (=exclusive BF) | 1299/14 735 (8.8%) | 1 (reference) | 1 (reference) | 2073/14 324 (14.5%) | 1 (reference) | 1 (reference) |
| FF(+), CF(−) | 1713/18 482 (9.3%) | 1.05 (0.98 to 1.13) | 1.01 (0.94 to 1.08) | 2935/17 985 (16.3%) | 1.13 (1.07 to 1.19) | 1.09 (1.03 to 1.15) |
| FF(−), CF(+) | 631/9960 (6.3%) | 0.72 (0.66 to 0.79) | 0.79 (0.72 to 0.87) | 1087/9857 (11.0%) | 0.76 (0.71 to 0.82) | 0.82 (0.77 to 0.88) |
| FF(+), CF(+) | 1184/16 314 (7.3%) | 0.82 (0.76 to 0.89) | 0.87 (0.81 to 0.95) | 2145/16 000 (13.4%) | 0.93 (0.88 to 0.98) | 0.97 (0.91 to 1.03) |
*Adjusted for sex, gestational age, birth weight, mother’s age, maternal smoking and alcohol, maternal and paternal education, family income and home speech stimulation at 1 month.
†Adjusted further for the introduction of complementary food. Boldface represents statistical significance (p<0.05).
aRR, adjusted risk ratio; BF, breast feeding; CF, complementary food; cRR, crude risk ratio; FF, formula feeding.