Table 1.
Characteristics of live births in Massachusetts during the 9-year period 2000–2008 for both the full-term analysis and AFT models.
| Characteristic | Term births | All births ≥ 22 weeks | ||||
|---|---|---|---|---|---|---|
| Percent of all births (n) | Mean birth weight ± SD (g) | Missing (n) | Percent of all births (n) | Mean birth weight ± SD (g) | Missing (n) | |
| Overall | (450,407) | 3,395 ± 502 | 3,251 | (462,400) | 3,391 ± 511 | 3,381 |
| Maternal race | 0 | 0 | ||||
| White | 72 (323,819) | 3,443 ± 496 | 72 (332,383) | 3,440 ± 503 | ||
| African American | 7 (33,775) | 3,257 ± 520 | 8 (34,803) | 3,246 ± 540 | ||
| Hispanic | 13 (60,339) | 3,297 ± 496 | 13 (62,029) | 3,313 ± 522 | ||
| Asian | 7 (31,491) | 3,234 ± 463 | 7 (32,174) | 3,229 ± 473 | ||
| Other | 0.3 (983) | 3,347 ± 505 | 0.3 (1,011) | 3,339 ± 527 | ||
| Maternal education (years) | 1,699 | 1,748 | ||||
| ≤ 8 | 3 (12,718) | 3,293 ± 492 | 3 (13,121) | 3,288 ± 501 | ||
| > 8–12 | 34 (154,723) | 3,319 ± 511 | 34 (159,307) | 3,313 ± 523 | ||
| 13–15 | 42 (187,792) | 3,407 ± 503 | 42 (192,246) | 3,455 ± 491 | ||
| ≥ 15 | 21 (94,994) | 3,457 ± 485 | 21 (97,726) | 3,403 ± 512 | ||
| Maternal age (years) | 1 | 1 | ||||
| ≤ 20 | 5 (22,900) | 3,219 ± 489 | 5 (23,618) | 3,211 ± 505 | ||
| 20–29 | 33 (146,668) | 3,335 ± 518 | 33 (150,538) | 3,330 ± 504 | ||
| 30–34 | 32 (142,033) | 3,427 ± 493 | 32 (145,720) | 3,424 ± 500 | ||
| 35–39 | 24 (106,542) | 3,459 ± 518 | 24 (109,365) | 3,455 ± 512 | ||
| > 39 | 7 (32,244) | 3,434 ± 518 | 7 (33,159) | 3,431 ± 530 | ||
| Maternal chronic conditions | ||||||
| Gestational diabetes | 3 (15,047) | 3,419 ± 633 | 1,342 | 3 (15,388) | 3,407 ± 562 | 1,420 |
| Nongestational diabetes | 1 (3,128) | 3,419 ± 633 | 1,342 | 1 (3,219) | 3,411 ± 649 | 1,420 |
| Previous infant ≥ 4,000 g | 1 (3,503) | 3,936 ± 508 | 1,342 | 1 (3,594) | 3,937 ± 511 | 1,420 |
| Hypertension | 3 (12,721) | 3,258 ± 567 | 1,342 | 3 (13,038) | 3,253 ± 575 | 1,420 |
| Lung disease | 3 (14,535) | 3,295 ± 531 | 1,342 | 3 (14,906) | 3,287 ± 547 | 1,420 |
| Previous preterm birth | 1 (4,331) | 3,080 ± 576 | 1,342 | 1 (4,475) | 3,070 ± 593 | 1,420 |
| Gestational age (weeks) | (450,407) | 39.0 ± 1.83 | 0 | (462,400) | 38.97 ± 1.95 | 0 |
| APNCU | 0 | 0 | ||||
| 1 (inadequate) | 9 (40,427) | 3,309 ± 507 | 9 (41,692) | 3,304 ± 518 | ||
| 2 (intermediate) | 8 (35,519) | 3,438 ± 476 | 8 (36,559) | 3,438 ± 477 | ||
| 3 (appropriate) | 48 (215,188) | 3,465 ± 463 | 48 (222,638) | 3,465 ± 465 | ||
| 4 (appropriate plus) | 35 (159,273) | 3,312 ± 539 | 35 (163,511) | 3,304 ± 555 | ||
| Mean household Income (US$) | (453,658) | 52,313 ± 21,566 | 0 | (462,400) | 52,296 ± 21,573 | 0 |
| Sex | 0 | 0 | ||||
| Male | 50 (226,589) | 3,452 ± 511 | 50 (232,720) | 3,447 ± 521 | ||
| Female | 50 (223,818) | 3,337 ± 486 | 50 (229,680) | 3,334 ± 494 | ||
| Parity (number of births) | (450,407) | 2 ± 2.7 | 0 | (462,400) | 2 ± 2.7 | 0 |
| Cigarettes per day during pregnancy (smokers) | (450,407) | 0.6 ± 2.7 | 642 | (462,400) | 0.7 ± 2.7 | 656 |
| Cigarettes per day before pregnancy (smokers) | (450,407) | 1.8 ± 5.1 | 616 | (462,400) | 1.8 ± 5.1 | 631 |
| Cumulative traffic density (average daily traffic counts) | (450,407) | 39.4 ± 23.5 | 0 | (462,400) | 39.2 ± 23.2 | 0 |
| Elevation (m) | (450,407) | 59.9 ± 68.3 | 0 | (462,400) | 60 ± 68.4 | 0 |
| Percent of open space | (450,407) | 12.0 ± 11.1 | 0 | (462,400) | 12.0 ± 11.1 | 0 |
| Season of birth | 0 | 0 | ||||
| Winter | 22 (97,982) | 3,379 ± 504 | 24 (108,896) | 3,378 ± 514 | ||
| Spring | 26 (117,669) | 3,402 ± 502 | 26 (118,182) | 3,399 ± 512 | ||
| Summer | 27 (121,629) | 3,399 ± 501 | 26 (121,917) | 3,396 ± 510 | ||
| Fall | 25 (113,127) | 3,393 ± 500 | 25 (113,405) | 3,390 ± 508 | ||
| Abbreviations: AFT, accelerated failure time; APNCU, Adequacy of Prenatal Care Utilization index. | ||||||