Table 1.
Cohort extraction: Baseline characteristics of the cohort
| Characteristic | Category | Singletons | Twins | Triplets or More | p-value |
|---|---|---|---|---|---|
| Gestational age | < 24 weeks | 20,277 (0.09%) | 4816 (0.71%) | 713 (2.48%) | |
| 24 weeks | 7458 (0.03%) | 1873 (0.28%) | 245 (0.85%) | <.0001 | |
| 25–26 weeks | 18,338 (0.08%) | 4694 (0.69%) | 676 (2.35%) | ||
| 27–28 weeks | 26,293 (0.12%) | 7876 (1.17%) | 1325 (4.62%) | ||
| 29–30 weeks | 40,542 (0.18%) | 13,722 (2.03%) | 2526 (8.80%) | ||
| 31–32 weeks | 81,279 (0.37%) | 31,474 (4.66%) | 4741 (16.51%) | ||
| 33–34 weeks | 224,024 (1.01%) | 77,985 (11.54%) | 6888 (23.99%) | ||
| 35–36 weeks | 603,530 (2.72%) | 149,048 (22.05%) | 3735 (13.01%) | ||
| Preterm but GA Unknown | 287,185 (1.30%) | 65,088 (9.63%) | 6312 (21.98%) | ||
| > 37 weeks | 20,839,514 (94.09%) | 319,393 (47.25%) | 1554 (5.41%) | ||
| Total | 22,148,440 (100.00%) | 675,969 (100.00%) | 28,716 (100.00%) | ||
| IUGR or SGA | Yes | 367,274 (1.66%) | 45,653 (6.75%) | 1856 (6.46%) | <.0001 |
| Sex | Female | 10,843,182 (49.02%) | 336,883 (49.89%) | 14,295 (49.83%) | <.0001 |
| Male | 11,274,557 (50.98%) | 338,380 (50.11%) | 14,393 (50.17%) | ||
| Total | 22,117,739 (100.00%) | 675,263 (100.00%) | 28,687 (100.00%) | ||
| Race/Ethnicity | White | 9,579,294 (52.79%) | 330,163 (59.27%) | 16,247 (70.15%) | <.0001 |
| Black | 2,461,724 (13.57%) | 85,412 (15.33%) | 2306 (9.96%) | ||
| Hispanic | 4,004,551 (22.07%) | 82,669 (14.84%) | 2435 (10.51%) | ||
| Asian/Pacific Islander | 881,691 (4.86%) | 23,992 (4.31%) | 833 (3.60%) | ||
| Native American | 124,300 (0.69%) | 3261 (0.59%) | 105 (0.45%) | ||
| Other | 1,094,195 (6.03%) | 31,571 (5.67%) | 1236 (5.34%) | ||
| Total | 18,145,755 (100.00%) | 557,068 (100.00%) | 23,161 (100.00%) | ||
| Primary expected payer | Medicare | 47,207 (0.21%) | 1380 (0.20%) | 21 (0.07%) | <.0001 |
| Medicaid | 9,344,270 (42.28%) | 223,397 (33.11%) | 5174 (18.05%) | ||
| Private insurance | 11,057,438 (50.03%) | 409,725 (60.72%) | 22,171 (77.36%) | ||
| Self-pay | 1,030,075 (4.66%) | 20,115 (2.98%) | 392 (1.37%) | ||
| No charge | 38,623 (0.17%) | 683 (0.10%) | 29 (0.10%) | ||
| Other | 582,632 (2.64%) | 19,455 (2.88%) | 874 (3.05%) | ||
| Total | 22,100,246 (100.00%) | 674,755 (100.00%) | 28,661 (100.00%) | ||
| Region of hospital | Northeast | 3,672,279 (16.58%) | 133,246 (19.71%) | 6370 (22.18%) | <.0001 |
| Midwest | 4,767,208 (21.52%) | 151,710 (22.44%) | 7074 (24.63%) | ||
| South | 8,412,784 (37.98%) | 243,999 (36.10%) | 9614 (33.48%) | ||
| West | 5,296,168 (23.91%) | 147,014 (21.75%) | 5657 (19.70%) | ||
| Total | 22,148,440 (100.00%) | 675,969 (100.00%) | 28,716 (100.00%) | ||
| Hospital type | Rural | 2,697,153 (12.28%) | 50,055 (7.48%) | 467 (1.66%) | <.0001 |
| Urban nonteaching | 8,756,542 (39.88%) | 231,462 (34.61%) | 6694 (23.80%) | ||
| Urban teaching | 10,502,357 (47.83%) | 387,322 (57.91%) | 20,962 (74.54%) | ||
| Total | 21,956,052 (100.00%) | 668,839 (100.00%) | 28,123 (100.00%) | ||
| Bed size of hospital | Small | 2,524,672 (11.50%) | 59,158 (8.84%) | 1227 (4.36%) | <.0001 |
| Medium | 5,918,612 (26.96%) | 165,112 (24.69%) | 5131 (18.24%) | ||
| Large | 13,512,768 (61.54%) | 444,569 (66.47%) | 21,765 (77.39%) | ||
| Total | 21,956,052 (100.00%) | 668,839 (100.00%) | 28,123 (100.00%) | ||
| Delivery type | NSVD | 15,728,662 (71.01%) | 192,045 (28.41%) | 1686 (5.87%) | <.0001 |
| CS | 6,419,778 (28.99%) | 483,924 (71.59%) | 27,030 (94.13%) | ||
| Total | 22,148,440 (100.00%) | 675,969 (100.00%) | 28,716 (100.00%) |