TABLE 2.
Feeding status at 4 mo postpartum in term and preterm infants and relative time to standing in the Upstate KIDS Study (2008–2010)1
| Term births |
Preterm births |
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| AF (95% CI) |
AF (95% CI) |
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| Median time to standing, mo | Unadjusted | Adjusted2 | Median time to standing, mo | Unadjusted | Adjusted2 | |
| Exclusive breastfeeding (reference) | 12 | — | — | 14 | — | — |
| Breastfeeding and formula feeding | 13 | 1.06 (0.99, 1.13) | 1.02 (0.95, 1.10) | 15 | 1.10 (0.90, 1.35) | 0.91 (0.74, 1.11) |
| Breastfeeding and solids | 11 | 0.94 (0.89, 1.00)3 | 0.93 (0.87, 0.99)3 | 13 | 0.99 (0.80, 1.22) | 0.93 (0.78, 1.12) |
| Breastfeeding, formula feeding, and solids | 12 | 0.97 (0.91, 1.03) | 0.98 (0.91, 1.04) | 14 | 1.02 (0.86, 1.20) | 0.96 (0.81, 1.14) |
| Exclusive formula feeding | 12 | 1.01 (0.96, 1.07) | 1.00 (0.94, 1.06) | 14 | 1.02 (0.87, 1.19) | 0.96 (0.81, 1.13) |
| Formula feeding and solids | 12 | 1.00 (0.96, 1.05) | 0.98 (0.94, 1.03) | 14 | 1.04 (0.91, 1.20) | 1.01 (0.88, 1.16) |
Information for term births in the unadjusted model was as follows—observations used: n = 3533; noncensored values: n = 1823; right-censored values: n = 1255; left-censored values: n = 120; and interval-censored values: n = 335. Information for term births in the adjusted model was as follows—observations used: n = 2011; noncensored values: n = 1315; right-censored values: n = 454; left-censored values: n = 49; and interval-censored values: n = 193. Information for preterm births in the unadjusted model was as follows—observations used: n = 737: noncensored values: n = 299; right-censored values: n = 320; left-censored values: n = 36; and interval-censored values: n = 82. Information for preterm births in the adjusted model was as follows—observations used: n = 396; noncensored values: n = 218; right-censored values: n = 114; left-censored values: n = 13; and interval-censored values: n = 51. Preterm was defined as birth at <37 wk of gestational age. AF, acceleration factor; Upstate KIDS Study, Upstate New York Infant Development Screening Program.
Accelerated failure time models were adjusted for maternal age, race, BMI, education, marital status, private insurance status, parity, and postpartum depression; paternal age and education; infant plurality, sex, rapid weight gain in the first 4 mo postpartum, Ages and Stages Questionnaire pass or fail status at 4 mo, daycare initiation, and conception via fertility treatment; and region via inverse probability weighting. P-interaction between preterm birth status and infant feeding for time to standing was 0.828.
Significant at α = 0.05.