TABLE 1.
Characteristics of the case and control women1
| Cases (n = 7392) | Controls (n = 56,304) | P value2 | |
| n (%) | n (%) | ||
| Maternal age | |||
| <20 y | 616 (8.3) | 4703 (8.3) | |
| 20–24 y | 1363 (18.4) | 10,600 (18.8) | |
| 25–29 y | 2025 (27.4) | 15,348 (27.3) | |
| 30–34 y | 2102 (28.4) | 16,470 (29.2) | |
| 35–39 y | 1064 (14.4) | 7754 (13.8) | |
| ≥40 y | 222 (3.0) | 1429 (2.5) | NS |
| Maternal race | |||
| White | |||
| Hispanic | 616 (8.3) | 4960 (8.8) | |
| Non-Hispanic | 4279 (57.9) | 33,477 (59.5) | |
| Unknown | 1404 (19.0) | 10,173 (18.1) | |
| Black | 838 (11.3) | 5707 (10.1) | |
| Asian | 175 (2.4) | 1466 (2.6) | |
| Other | 37 (0.5) | 303 (0.5) | |
| Unknown | 43 (0.6) | 218 (0.4) | 0.0005 |
| Maternal education | |||
| <12 y | 1092 (14.8) | 7972 (14.2) | |
| 12 y | 2369 (32.0) | 17,433 (31.0) | |
| >12 y | 3805 (51.5) | 30,102 (53.5) | |
| Unknown | 126 (1.7) | 797 (1.4) | 0.01 |
| Primary payer | |||
| Medicaid | 2105 (28.5) | 14,429 (25.6) | |
| HMO | 2502 (33.9) | 21,408 (38.0) | |
| Private insurance | 2578 (34.9) | 18,669 (33.2) | |
| Self-pay | 111 (1.5) | 1078 (1.9) | |
| Unknown | 96 (1.3) | 720 (1.3) | <0.0001 |
| Tobacco use | |||
| No | 6159 (83.3) | 47,019 (83.5) | |
| Yes | 1172 (15.8) | 8848 (15.7) | |
| Unknown | 61 (0.8) | 437 (0.8) | NS |
| Alcohol use | |||
| No | 7249 (98.1) | 55,323 (98.3) | |
| Yes | 82 (1.1) | 535 (0.9) | |
| Unknown | 61 (0.8) | 446 (0.8) | NS |
| Infant sex | |||
| Male | 3806 (51.5) | 28,655 (50.9) | |
| Female | 3584 (48.5) | 27,648 (49.1) | |
| Unknown | 2 (0.0) | 1 (0.0) | NS |
| Birth weight | |||
| <1500 g | 428 (5.8) | 418 (0.7) | |
| 1500 to <2500 g | 836 (11.3) | 2158 (3.8) | |
| ≥2500 g | 6120 (82.8) | 53,702 (95.4) | |
| Unknown | 80 (0.1) | 26 (0.1) | <0.0001 |
| Gestational age | |||
| <32 wk | 459 (6.2) | 669 (1.2) | |
| 32 to <37 wk | 1039 (14.1) | 3806 (6.8) | |
| ≥37 wk | 5885 (79.6) | 51,772 (91.9) | |
| Unknown | 9 (0.1) | 57 (0.1) | <0.0001 |
| Parity | |||
| 0 | 3054 (41.3) | 22,646 (40.2) | |
| 1 | 2382 (32.2) | 19,098 (33.9) | |
| ≥2 | 1955 (26.4) | 14,559 (25.9) | |
| Unknown | 1 (0.0) | 1 (0.0) | 0.02 |
| BMI | |||
| <19 kg/m2, underweight | 569 (7.7) | 4424 (7.9) | |
| 19–24 kg/m2, normal weight | 3902 (52.8) | 30,561 (54.3) | |
| 25–29 kg/m2, overweight | 1605 (21.7) | 12,495 (22.2) | |
| 30–39 kg/m2, obese | 1084 (14.7) | 7496 (13.3) | |
| ≥40 kg/m2, morbidly obese | 232 (3.1) | 1328 (2.4) | <0.0001 |
1
HMO, health maintenance organization.
2
Comparison of proportions between cases and controls was made by using the chi-square test; unknown values were not included in the calculation of P values.