Table 3.
The results of univariate logistic analyses for the selection of formula feeding presented as birth year adjusted odds ratios and 95% confidence intervals
| 0 months | 3 months | 6 months | ||||
|---|---|---|---|---|---|---|
| First-born | Second-born | First-born | Second-born | First-born | Second-born | |
| Gestational age | ||||||
| <37 weeks (reference: ≥37 weeks) | 1.74 (1.38–2.19) | 1.67 (1.33–2.10) | 1.27 (1.05–1.55) | 1.25 (1.03–1.52) | 1.38 (1.13–1.69) | 1.34 (1.10–1.64) |
| Birthweight | ||||||
| <2,000 g (reference: ≥2,000 g) | 1.50 (1.11–2.01) | 1.68 (1.29–2.18) | 1.07 (0.82–1.38) | 1.14 (0.91–1.43) | 1.01 (0.78–1.31) | 1.09 (0.86–1.37) |
| Maternal age at twin birth | ||||||
| ≥35 years (reference: <35 years) | 1.44 (1.05–1.98) | 1.46 (1.06–2.00) | 1.28 (0.97–1.68) | 1.35 (1.03–1.77) | 0.99 (0.75–1.30) | 1.06 (0.80–1.40) |
| Birth injury | ||||||
| Yes (reference: no) | 0.93 (0.75–1.16) | 0.89 (0.72–1.11) | 0.94 (0.78–1.12) | 0.87 (0.73–1.05) | 1.05 (0.87–1.26) | 0.95 (0.78–1.14) |
| Sex | ||||||
| Male (reference: female) | 0.78 (0.63–0.97) | 0.91 (0.74–1.13) | 0.96 (0.80–1.14) | 1.05 (0.88–1.26) | 1.07 (0.89–1.29) | 1.11 (0.92–1.33) |
| Parity | ||||||
| Primipara (reference: multipara) | 1.15 (0.92–1.44) | 1.12 (0.90–1.40) | 0.98 (0.82–1.18) | 0.95 (0.79–1.14) | 1.12 (0.93–1.36) | 1.09 (0.90–1.32) |
| Zygosity | ||||||
| Monozygotic (reference: dizygotic) | 0.89 (0.70–1.12) | 0.91 (0.72–1.15) | 1.10 (0.91–1.34) | 1.11 (0.91–1.35) | 1.25 (1.02–1.52) | 1.17 (0.96–1.43) |
| Presentation | ||||||
| Non-vertex (reference: vertex) | 0.92 (0.67–1.26) | 1.30 (1.03–1.65) | 1.02 (0.79–1.32) | 1.11 (0.91–1.35) | 1.25 (0.95–1.63) | 1.08 (0.88–1.32) |
| Placentation | ||||||
| Monochorionic (reference: dichorionic) | 0.82 (0.62–1.09) | 0.84 (0.64–1.12) | 0.87 (0.69–1.10) | 0.87 (0.69–1.10) | 0.98 (0.78–1.23) | 0.93 (0.74–1.17) |
| Caesarean section | ||||||
| Yes (reference: no) | 1.20 (0.94–1.54) | 1.27 (0.99–1.63) | 1.03 (0.84–1.26) | 1.07 (0.88–1.31) | 1.11 (0.90–1.36) | 1.12 (0.91–1.37) |
| Fertility treatment | ||||||
| Yes (reference: no) | 1.32 (0.95–1.84) | 1.29 (0.92–1.79) | 0.96 (0.74–1.25) | 0.90 (0.69–1.17) | 1.27 (0.98–1.65) | 1.27 (0.98–1.65) |
| Use of incubator | ||||||
| Yes (reference: no) | 1.49 (1.20–1.86) | 1.89 (1.51–2.36) | 1.20 (1.00–1.44) | 1.33 (1.11–1.60) | 1.12 (0.93–1.35) | 1.23 (1.02–1.49) |
| Previous abortion | ||||||
| Yes (reference: no) | 1.02 (0.78–1.32) | 0.95 (0.73–1.24) | 1.13 (0.91–1.40) | 1.06 (0.85–1.32) | 0.99 (0.79–1.23) | 0.94 (0.75–1.18) |
| Neonatal asphyxia | ||||||
| Severe or mild (reference: no) | 1.21 (0.91–1.61) | 1.54 (1.20–1.98) | 0.92 (0.72–1.17) | 1.19 (0.95–1.49) | 0.95 (0.74–1.23) | 1.10 (0.87–1.39) |
| Group | ||||||
| School applicants (reference: maternal associations) | 0.85 (0.57–1.27) | 0.77 (0.51–1.16) | 1.21 (0.91–1.60) | 1.19 (0.90–1.58) | 1.06 (0.81–1.39) | 1.00 (0.76–1.32) |
Birth year was treated as a dichotomized variable (1968–1984 vs 1985–2003). The comparison group is full or partial breast-feeding. Significant 95% confidence intervals are shown in bold