Table 1 Characteristics of the study population recruited from three US cities during 2000-4
Population characteristics | PTD | SGAa | Birth weight (g) | |||
|---|---|---|---|---|---|---|
n | % | % | % | Mean | SD | |
Total population | 2039 | 100 | 9 | 5 | 3382 | 586 |
Maternal race/ethnicity | ||||||
Non-Hispanic white | 1169 | 57 | 7 | 5 | 3486 | 596 |
Non-Hispanic black | 609 | 30 | 12 | 7 | 3167 | 545 |
Hispanic | 185 | 9 | 9 | 6 | 3427 | 632 |
Other | 73 | 4 | 7 | -- | 3400 | 459 |
Missing | 3 | |||||
Maternal age (years) | ||||||
< 25 | 599 | 29 | 11 | 7 | 3255 | 558 |
25-29 | 657 | 32 | 8 | 6 | 3393 | 572 |
30-34 | 564 | 28 | 7 | 4 | 3486 | 587 |
≥35 | 219 | 11 | 11 | 6 | 3425 | 642 |
Highest maternal education level | ||||||
High school or less | 573 | 28 | 13 | 9 | 3235 | 616 |
Some college | 440 | 22 | 10 | 5 | 3340 | 600 |
College degree or higher | 1025 | 50 | 7 | 4 | 3482 | 544 |
Maternal smoking | ||||||
Yes | 99 | 5 | 16 | 12 | 3073 | 578 |
No | 1940 | 95 | 9 | 5 | 3398 | 583 |
Maternal alcohol use | ||||||
Yes | 32 | 2 | 9 | 6 | 3410 | 702 |
No | 2007 | 98 | 6 | 6 | 3381 | 585 |
Pre-pregnancy BMI (kg/m2) | ||||||
< 19.8 | 232 | 11 | 8 | 9 | 3291 | 535 |
19.8-25.9 | 1016 | 50 | 8 | 5 | 3410 | 553 |
26.0-29.9 | 333 | 16 | 7 | 6 | 3421 | 535 |
> 29.9 | 407 | 20 | 14 | 5 | 3349 | 713 |
Missing | 51 | 3 | 10 | 16 | 3255 | 771 |
Vitamin use | ||||||
Yes | 1027 | 50 | 7 | 5 | 3461 | 573 |
No | 1012 | 50 | 11 | 7 | 3302 | 590 |
Caffeine intake (mg/day) | ||||||
None | 519 | 25 | 9 | 4 | 3410 | 613 |
1-150 | 468 | 23 | 8 | 5 | 3385 | 557 |
151-300 | 387 | 19 | 11 | 6 | 3344 | 617 |
> 300 | 665 | 33 | 9 | 7 | 3380 | 567 |
Marital status | ||||||
Married | 1390 | 68 | 7 | 5 | 3466 | 536 |
Not married | 648 | 32 | 13 | 8 | 3200 | 646 |
Missing | 1 | |||||
Parity | ||||||
Nulliparous | 991 | 49 | 10 | 6 | 3323 | 591 |
Parous | 1048 | 51 | 8 | 4 | 3438 | 577 |
Employed during past 4 months | ||||||
Yes | 1430 | 70 | 9 | 5 | 3372 | 580 |
No | 608 | 30 | 9 | 7 | 3406 | 602 |
Annual household income ($) | ||||||
< 30,000 | 637 | 31 | 12 | 7 | 3245 | 629 |
30,001-60,000 | 535 | 26 | 7 | 7 | 3437 | 545 |
60,001-80,000 | 321 | 16 | 6 | 5 | 3460 | 498 |
> 80,000 | 465 | 23 | 8 | 3 | 3504 | 571 |
Missing | 81 | 4 | 20 | 10 | 3078 | 614 |
Recreational activityb | ||||||
Yes | 1109 | 54 | 9 | 6 | 3423 | 572 |
No | 930 | 46 | 10 | 5 | 3332 | 600 |
Vigorous recreational activityc | ||||||
Yes | 401 | 20 | 8 | 7 | 3412 | 559 |
No | 1638 | 80 | 9 | 5 | 3374 | 593 |
Swimming | ||||||
Yes | 651 | 58 | 6 | 6 | 3471 | 549 |
No | 1388 | 32 | 10 | 6 | 3340 | 599 |
Infant gender | ||||||
Male | 1045 | 51 | 9 | 7 | 3419 | 585 |
Female | 994 | 49 | 9 | 5 | 3343 | 586 |
Study site | ||||||
Site 1 | 929 | 46 | 6 | 5 | 3459 | 581 |
Site 2 | 761 | 37 | 11 | 6 | 3329 | 593 |
Site 3 | 349 | 17 | 13 | 8 | 3294 | 562 |