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Table 2 Population characteristics in Fresno County, 2009–2012 (N = 53,843)

From: Environmental pollution and social factors as contributors to preterm birth in Fresno County

Population Characteristics n (%) Pollution Burden Quintile
1st 2nd 3rd 4th 5th
Race/ethnicity
 White non-Hispanic 10,620 (19.7) 139 (35.0) 583 (53.5) 2042 (38.3) 4113 (20.0) 3665 (14.0)
 Hispanic 32,302 (60.0) 212 (53.4) 357 (32.8) 2186 (41.0) 12,314 (59.7) 17,210 (65.5)
 Black 3095 (5.8) * 17 (1.6) 226 (4.2) 1159 (5.6) 1689 (6.4)
 Asian 5675 (10.5) * 100 (9.2) 512 (9.6) 2141 (10.4) 2899 (11.0)
 American Indian/Alaska native 546 (1.0) 19 (4.8) * 70 (1.3) 201 (1.0) 245 (0.9)
 Hawaiian/Pacific Islander 70 (0.1) * * * 40 (0.2) 19 (0.1)
 Other race 581 (1.1) * * 171 (3.2) 244 (1.2) 155 (0.6)
 Two or more races 954 (1.8) * * 122 (2.3) 406 (2.0) 395 (1.5)
Infant sex
 Male 27,354 (50.8) 208 (52.4) 569 (52.3) 2675 (50.1) 10,437 (50.6) 13,391 (51.0)
 Female 26,489 (49.2) 189 (47.6) 520 (47.8) 2663 (49.9) 10,180 (49.4) 12,886 (49.0)
Maternal age at delivery (years)
  < 18 2263 (4.2) 19 (4.8) 22 (2.0) 132 (2.5) 801 (3.9) 1288 (4.9)
 18–34 45,552 (84.6) 340 (84.6) 864 (79.3) 4420 (82.8) 17,506 (84.9) 22,331 (85.0)
  > 34 6028 (11.2) 38 (9.6) 203 (18.6) 786 (14.7) 2311 (11.2) 2658 (10.1)
Maternal education (years)
  < 12 16,607 (30.8) 85 (21.4) 132 (12.1) 990 (18.6) 5877 (28.5) 9522 (36.2)
 12 15,195 (28.2) 159 (40.1) 232 (21.3) 1275 (23.9) 6063 (29.4) 7456 (28.4)
  > 12 22,041 (40.9) 153 (38.5) 725 (66.6) 3073 (57.6) 8678 (42.1) 9299 (35.4)
WIC participanta
 Yes 39,404 (73.2) 287 (72.4) 436 (40.0) 2760 (51.7) 15,190 (73.7) 20,723 (79.0)
 No 14,439 (26.8) 150 (37.8) 655 (60.2) 2532 (47.4) 5305 (25.7) 5192 (9.8)
Payer for delivery costs
 Private insurance 13,949 (25.9) 150 (37.8) 655 (60.2) 2532 (47.4) 5305 (25.7) 5192 (9.8)
 Medi-Cal 39,040 (72.5) 222 (55.9) 399 (36.6) 2730 (51.1) 15,015 (72.8) 20,665 (78.6)
 Other government payer 651 (1.2) * 22 (2.0) 20 (0.4) 36 (0.2) 43 (0.2)
 Self-pay 134 (0.3) * * 50 (0.9) 230 (1.1) 346 (1.3)
 Other payer 2 (0.0) * * * * *
 No pay 67 (0.1) * * * 31 (0.2) 30 (0.1)
Place of mother’s birth
 United States 35,911 (66.7) 317 (79.9) 825 (75.8) 3881 (72.7) 13,930 (67.6) 16,854 (64.1)
 Mexico 13,174 (24.5) 68 (17.1) 121 (11.1) 737 (13.8) 4865 (23.6) 7382 (28.1)
 Other 4758 (8.8) 12 (3.0) 143 (13.1) 720 (13.5) 1823 (8.8) 2041 (7.8)
Maternal conditionsb
 Diabetes, preexisting 565 (1.1) * * 33 (0.6) 220 (1.7) 302 (1.2)
 Diabetes, gestational 4875 (9.1) 42 (10.6) 86 (7.9) 429 (8.0) 1796 (8.7) 2517 (9.6)
 Hypertension, preexisting 915 (1.7) * * 103 (1.9) 351 (1.7) 436 (1.7)
  Without preeclampsia 649 (1.2) * * 75 (1.4) 254 (1.2) 298 (1.1)
  With preeclampsia 266 (0.5) * * 28 (0.5) 97 (0.5) 138 (0.5)
 Hypertension, gestational 3004 (5.6) * 47 (4.3) 294 (5.5) 1083 (5.3) 1564 (6.0)
  Without preeclampsia 1224 (2.3) * 21 (1.9) 140 (2.6) 424 (2.1) 629 (2.4)
  With preeclampsia 1780 (3.3) * 26 (2.4) 154 (2.9) 659 (3.2) 936 (3.6)
 Infection 7402 (13.8) 45 (11.3) 102 (9.4) 562 (10.5) 2805 (13.6) 3789 (14.8)
 Anemia 4187 (7.8) 31 (7.8) 73 (6.7) 423 (7.9) 1887 (9.2) 2725 (10.4)
 Mental Illness 1231 (2.3) * 35 (3.2) 155 (2.9) 680 (3.3) 954 (3.6)
 Reported Smoking 276 (0.5) 27 (6.8) 89 (8.2) 451 (8.5) 1664 (8.1) 1947 (7.4)
 Reported Drug Abuse 1835 (3.4) * * 94 (1.8) 423 (2.1) 697 (2.7)
 Reported Alcohol Dependence 5147 (9.6)      
Trimester when prenatal care began
 1st 45,632 (84.8) 307 (77.3) 940 (86.3) 4659 (87.3) 17,575 (85.2) 22,032 (83.9)
 2nd 4846 (9.0) 66 (16.6) 93 (8.5) 341 (6.4) 1726 (8.4) 2619 (10.0)
 3rd 696 (1.3) * 20 (1.8) 76 (1.4) 246 (1.2) 340 (1.3)
Multiparous sample 35,638 261 708 3354 13,591 17,651
 Previous Cesarean-section 9179 (25.8) 78 (29.9) 208 (29.4) 886 (26.4) 3520 (25.9) 4462 (25.3)
 Previous Preterm Birth 403 (1.1) * * 48 (1.4) 168 (1.2) 178 (1.0)
Interpregnancy Interval c
  < 6 months 2283 (6.4) 21 (8.1) 28 (4.0) 174 (5.2) 853 (6.3) 1207 (6.8)
 6–23 months 11,683 (32.8) 76 (29.1) 271 (38.3) 1142 (34.1) 4407 (32.4) 5748 (32.6)
 24–59 months 13,671 (38.4) 112 (42.9) 253 (35.7) 1233 (36.8) 5208 (38.3) 6843 (38.8)
  > 59 months 5371 (15.1) 34 (13.0) 95 (13.4) 527 (15.7) 2099 (15.4) 2610 (14.8)
  1. *n < 16
  2. aWIC Participation – Women, Infants and Children food and nutrition service
  3. bDetermined by ICD-9 codes in maternal discharge records: preexisting diabetes (ICD-9 code 250 and 648.0), gestational diabetes (648.8), preexisting hypertension (642.0, 642.1, 642.2, 642.7), gestational hypertension (642.3), preeclampsia/eclampsia (642.4, 642.4, 642.6), infection (646.5, 646.6, 647), anemia (648.2), mental illness (648.4)
  4. cNumber of months between the delivery date of the preceding live birth and the conception date of the index pregnancy