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Table 1 Characteristics of the study population recruited from three US cities during 2000-4

From: The relationship between water intake and foetal growth and preterm delivery in a prospective cohort study

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
  1. aTerm births only
  2. bAny recreational physical activity or exercise, such as brisk walking, jogging, swimming, biking, tennis, soccer, or dancing
  3. cAny recreational physical activity or exercise, such as brisk walking, jogging, swimming, biking, tennis, soccer, or dancing that caused large increases in breathing and heart rate
  4. SGA = small for gestational age; PTD = preterm delivery; SD = standard deviation; BMI = body mass index