Characteristics of the study population by cause of death category
| Characteristic | Total (n=778) | Unexplained* (n=276) | Unintentional asphyxia (n=502) |
| Age (n, %) | |||
| Less than 2 months | 232 (29.8) | 86 (31.2) | 146 (29.1) |
| 2–4 months | 369 (47.4) | 130 (47.1) | 239 (47.6) |
| 5–11 months | 177 (22.8) | 60 (21.7) | 117 (23.3) |
| Race/ethnicity (n, %) | |||
| White, non-Hispanic | 269 (34.6) | 93 (33.7) | 176 (35.1) |
| Black, non-Hispanic | 299 (38.4) | 104 (37.7) | 195 (38.8) |
| Hispanic | 135 (17.4) | 49 (17.8) | 86 (17.1) |
| Other, non-Hispanic | 55 (7.1) | 23 (8.3) | 32 (6.4) |
| Unknown | 20 (2.6) | 7 (2.5) | 13 (2.6) |
| Sex (n, %) | |||
| Male | 458 (58.9) | 145 (52.5) | 313 (62.4) |
| Female | 320 (41.1) | 131 (47.5) | 189 (37.7) |
| Gestational age in weeks (n, %) | |||
| ≥37 | 593 (76.2) | 206 (74.6) | 387 (77.1) |
| <37 | 155 (19.9) | 58 (21.0) | 97 (19.3) |
| Unknown | 1 (0.1) | 1 (0.4) | 0 (0) |
| Missing | 29 (3.7) | 11 (4.0) | 18 (3.6) |
| Birth weight in grams (n, %) | |||
| ≥2500 | 629 (80.9) | 219 (79.4) | 410 (81.7) |
| <2500 | 149 (19.2) | 57 (20.7) | 92 (18.3) |
| Maternal age (n, %) | |||
| <20 | 86 (11.1) | 25 (9.1) | 61 (12.2) |
| 20–25 | 320 (41.1) | 113 (40.9) | 207 (41.2) |
| 26–35 | 293 (37.7) | 104 (37.7) | 189 (37.7) |
| >35 | 50 (6.4) | 23 (8.3) | 27 (5.4) |
| Missing | 29 (3.7) | 11 (4.0) | 18 (3.6) |
| Maternal education level (n, %) | |||
| Less than high school | 189 (24.3) | 68 (24.6) | 121 (24.1) |
| High school graduate | 318 (40.9) | 97 (35.1) | 221 (44.0) |
| Some college | 186 (23.9) | 80 (29.0) | 106 (21.1) |
| College graduate | 45 (5.8) | 16 (5.8) | 29 (5.8) |
| Unknown | 11 (1.4) | 4 (1.5) | 7 (1.4) |
| Missing | 29 (3.7) | 11 (4.0) | 18 (3.6) |
*Includes cases with undetermined, unknown, sudden infant death syndrome (SIDS) and sudden unexpected infant death (SUID) as the underlying cause documented on the death certificate.