Background
Methods
Study design and population
Assessment of foetal growth and PTD
Assessment of exposures and confounding factors
Statistical analysis
Results
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 |
Birth weight
Follow-up data | Average of baseline and follow-up data | ||||||
---|---|---|---|---|---|---|---|
Unadjusted | Adjusteda
| Adjusteda
| |||||
Exposure | n (%) | ß | 95% CI | ß | 95% CI | ß | 95% CI |
Bottled water | |||||||
None | 448 (25%) | Ref | Ref | Ref | |||
Any | 1329 (75%) | 12 | (-38, 63) | 31 | (-20, 82) | 43 | (-27, 113) |
Cold tap water (ounces)b
| |||||||
0-27 | 424 (24%) | Ref | Ref | Ref | |||
> 27-53 | 455 (25%) | 12 | (-50, 74) | 9 | (-53, 72) | 25 | (-38, 88) |
> 53-91 | 444 (25%) | 74 | (11, 136) | 52 | (-11, 116) | 44 | (-19, 107) |
> 91 | 453 (26%) | 77 | (14, 139) | 49 | (-14, 111) | 65 | (2, 128) |
Per 20 ounce | 12.3 | (3.9, 20.7) | 8.5 | (0.1, 16.9) | 8.5 | (-1.5, 18.5) | |
Total tap water (ounces)b
| |||||||
0-30 | 443 (25%) | Ref | Ref | Ref | |||
> 30-61 | 445 (25%) | 41 | (-21, 103) | 44 | (-18, 106) | 10 | (-52, 73) |
> 61-96 | 496 (28%) | 100 | (40, 161) | 78 | (17, 139) | 34 | (-30, 97) |
> 96 | 392 (22%) | 85 | (21, 149) | 43 | (-21, 107) | 46 | (-17, 109) |
Per 20 ounce | 12.0 | (4.0, 20.1) | 6.8 | (-1.3, 15.0) | 5.3 | (-4.3, 15.1) | |
Total water (ounces)b
| |||||||
0-51 | 452 (25%) | Ref | Ref | Ref | |||
> 51-78 | 439 (25%) | 60 | (-1, 122) | 27 | (-34, 87) | 10 | (-50, 71) |
> 78-114 | 442 (25%) | 67 | (5, 128) | 39 | (-22, 99) | 55 | (-6, 116) |
> 114 | 441 (25%) | 83 | (21, 145) | 50 | (-11, 111) | 37 | (-25, 98) |
Per 20 ounce | 9.8 | (1.6, 18.1) | 7.3 | (-0.8, 15.5) | 5.2 | (-4.7, 15.2) |
SGA
Follow-up data | Average of baseline and follow-up data | |||
---|---|---|---|---|
Exposure | n (%) | Unadjusted RR (95% CI) | Adjusted RR (95% CI)b
| Adjusted RR (95% CI)b
|
Bottled water | ||||
None | 448 (26%) | 1 | 1 | 1 |
Any | 1258 (74%) | 1.1 (0.7, 1.7) | 0.9 (0.5, 1.4) | 1.4 (0.6, 3.0) |
Cold tap water (ounces)c
| ||||
0-27 | 403 (24%) | 1 | 1 | 1 |
> 27-53 | 439 (26%) | 0.9 (0.5, 1.5) | 1.2 (0.6, 2.3) | 1.1 (0.6, 2.2) |
> 53-91 | 429 (25%) | 0.9 (0.5, 1.6) | 1.3 (0.7, 2.4) | 1.4 (0.7, 2.6) |
> 91 | 439 (26%) | 0.7 (0.4, 1.2) | 0.9 (0.5, 1.9) | 1.1 (0.5, 2.1) |
Per 20 ounce | 1.0 (0.9, 1.0) | 1.0 (0.9, 1.1) | 1.0 (0.9, 1.1) | |
Total tap water (ounces)c
| ||||
0-30 | 423 (25%) | 1 | 1 | 1 |
> 30-61 | 426 (25%) | 0.7 (0.4, 1.3) | 0.9 (0.5, 1.7) | 1.2 (0.6, 2.2) |
> 61-96 | 476 (28%) | 0.7 (0.4, 1.2) | 0.8 (0.5, 1.6) | 1.3 (0.7, 2.6) |
> 96 | 380 (22%) | 0.7 (0.4, 1.2) | 0.9 (0.5, 1.9) | 1.1 (0.6, 2.2) |
Per 20 ounce | 1.0 (0.9, 1.1) | 1.0 (0.9, 1.1) | 1.0 (0.9, 1.1) | |
Total water (ounces)
c
| ||||
0-51 | 434 (25%) | 1 | 1 | 1 |
> 51-78 | 418 (25%) | 0.7 (0.4, 1.2) | 0.8 (0.4, 1.4) | 0.9 (0.5, 1.6) |
> 78-114 | 424 (25%) | 0.6 (0.3, 1.0) | 0.6 (0.3, 1.0) | 0.5 (0.2, 1.0) |
> 114 | 427 (25%) | 0.8 (0.5, 1.4) | 0.9 (0.5, 1.6) | 1.0 (0.6, 1.8) |
Per 20 ounce | 1.0 (0.9, 1.1) | 1.0 (0.9, 1.1) | 1.0 (0.9, 1.1) |
PTD
Follow-up data | Average of baseline and follow-up data | |||
---|---|---|---|---|
Exposure | n (%) | Unadjusted RR (95% CI) | Adjusted RR (95% CI)a
| Adjusted RR (95% CI)a
|
Bottled water | ||||
None | 483 (25%) | 1 | 1 | 1 |
Any | 1458 (75%) | 1.2 (0.9, 1.8) | 1.2 (0.8, 1.8) | 0.8 (0.5, 1.4) |
Cold tap water (ounces)b
| ||||
0-27 | 472 (24%) | 1 | 1 | 1 |
> 27-53 | 494 (25%) | 0.8 (0.5, 1.2) | 0.8 (0.5, 1.3) | 0.9 (0.6, 1.4) |
> 53-91 | 485 (25%) | 0.9 (0.6, 1.3) | 0.9 (0.6, 1.4) | 0.9 (0.6, 1.4) |
> 91 | 490 (25%) | 0.8 (0.5, 1.1) | 0.8 (0.5, 1.3) | 1.0 (0.6, 1.5) |
Per 20 ounce | 1.0 (0.9, 1.0) | 0.9 (0.7, 1.3) | 0.9 (0.6, 1.3) | |
Total tap water (ounces)b
| ||||
0-30 | 493 (25%) | 1 | 1 | 1 |
> 30-61 | 483 (25%) | 0.8 (0.5, 1.2) | 0.8 (0.5, 1.2) | 1.0 (0.6, 1.5) |
> 61-96 | 535 (28%) | 0.7 (0.5, 1.1) | 0.8 (0.5, 1.2) | 1.2 (0.8, 1.9) |
> 96 | 429 (22%) | 0.9 (0.6, 1.3) | 1.0 (0.6, 1.5) | 0.9 (0.6, 1.4) |
Per 20 ounce | 1.0 (0.9, 1.0) | 0.9 (0.7, 1.2) | 0.9 (0.6, 1.3) | |
Total water (ounces)b
| ||||
0-51 | 491 (25%) | 1.0 | 1.0 | 1.0 |
> 51-78 | 478 (25%) | 1.0 (0.7, 1.6) | 1.2 (0.7, 1.9) | 1.1 (0.7, 1.7) |
> 78-114 | 481 (25%) | 1.0 (0.7, 1.6) | 1.1 (0.7, 1.8) | 1.0 (0.6, 1.5) |
> 114 | 478 (25%) | 1.2 (0.8, 1.8) | 1.4 (0.9, 2.2) | 1.2 (0.8, 1.9) |
Per 20 ounce | 1.0 (1.0, 1.1) | 1.1 (0.9, 1.4) | 1.1 (0.8, 1.5) |