Table 1. Baseline Characteristics.
| Characteristic | Full Cohort (N = 290 992) |
P-VLBW Subcohorta (N = 2015) |
|---|---|---|
| Maternal age, mean (SD), y | 27.16 (5.34) | 27.08 (5.74) |
| Birth weight, mean (SD), g | 3294.64 (539.96) | 980.89 (300.56) |
| Gestational age, mean (SD), wk | 38.38 (1.87) | 26.87 (2.40) |
| Preeclampsia, No. (%) | 8996 (3.09) | 469 (23.28) |
| Maternal race/ethnicity, No. (%)b | ||
| White | 236 443 (81.4) | 1569 (77.98) |
| Black | 1453 (0.50) | 23 (1.14) |
| Asian, Pacific Islander, and American Indian | 6824 (2.35) | 56 (2.78) |
| Hispanic | 32 265 (11.11) | 256 (12.87) |
| Other or unknown | 13 475 (4.64) | 105 (5.22) |
| Infant sex, male, No. (%)c | 148 983 (51.23) | 1099 (54.57) |
| Alcohol use, No. (%)d | 5141 (1.77) | 110 (5.46) |
| Substance abuse, No. (%)d | 801 (0.28) | 54 (2.68) |
| Tobacco exposure, No. (%)d | 18 685 (6.42) | 266 (12.20) |
| Multiple gestations, No. (%)d | 8907 (3.06) | 537 (26.65) |
Abbreviation: P-VLBW, preterm very low-birth-weight.
a
Preterm very low birth weight was considered younger than 31 weeks’ gestational age and weighing less than 1500 g.
b
Five hundred thirty-two births (0.18%) in the full cohort and 3 births (0.15%) in the P-VLBW subcohort did not have maternal race/ethnicity reported.
c
One hundred seventy-four births (0.15%) in the full cohort and 1 birth (0.05%) in the P-VLBW subcohort had missing infant sex.
d
Self-reported parameters.