Table 1.
Infant characteristics
| Preterm (N = 40) | Term (N = 89) | |
|---|---|---|
| Baseline characteristics | ||
| Birth weight (g), median (range) | 845 (540–2508) | 3365 (1820–4440) |
| Gestational age (weeks), median (range) | 27 (23–36) | 39 (37–42) |
| Female sex, n (%) | 28 (70) | 46 (52) |
| Multiple gestation, n (%) | 13 (33) | 7 (8) |
| Race, n (%) | ||
| White | 19 (48) | 45 (51) |
| Black or African American | 20 (50) | 28 (31) |
| Asian | 0 (0) | 2 (2) |
| Native Hawaiian or other Pacific Islander | 0 (0) | 1 (1) |
| Unknown or not reported | 1 (3) | 13 (15) |
| Hispanic or Latino, n (%) | 0 (0) | 5 (6) |
| Mother hospital days prior to delivery, median (range) | 3.5 (0–15) | 0 (0–6) |
| Labor prior to delivery, n (%) | 21 (53) | 62 (70) |
| Prolonged rupture of membranes > 18 h, n (%) | 6 (17) | 14 (17) |
| Cesarean section, n (%) | 30 (86) | 36 (43) |
| Clinical factors at time of sampling | ||
| Age at sampling (d), median (range) | 42 (1–252) | 1 (0–122) |
| Location, n (%) | ||
| Neonatal intensive care unit | 40 (100) | 12 (13) |
| Mother’s room | 0 (0) | 77 (87) |
| Type of bed at time of sampling, n (%) | ||
| Open crib | 18 (45) | 87 (98) |
| Warmer bed | 1 (3) | 2 (2) |
| Isolette | 21 (53) | 0 (0) |
| Diet, n (%) | ||
| Mostly breast milk | 19 (48) | 56 (63) |
| Mostly formula | 15 (38) | 33 (37) |
| Any receipt of breast milk | 32 (80) | 63 (71) |
| No feeds prior to sampling | 6 (15) | 0 (0) |
| Primary feeding route, n (%) | ||
| Breastfeeding | 1 (3) | 50 (56) |
| Bottle | 7 (18) | 38 (43) |
| Feeding tube | 26 (65) | 1 (1) |
| No feeds prior to sampling | 6 (15) | 0 (0) |
| Previous antibiotic exposure, n (%) | 37 (93) | 15 (17) |