TABLE 1.
Distribution of maternal characteristics of the sample populationa by county and race, 1999–2001
| Wake County
|
Durham County
|
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|---|---|---|---|---|---|---|---|---|
| White
|
Black
|
White
|
Black
|
|||||
| Variablesb | N (%) | % preterm | N (%) | % preterm | N (%) | % preterm | N (%) | % preterm |
| Maternal age | ||||||||
| < 20 years | 458 (2.8) | 8.7 | 726 (13.1) | 10.9 | 407 (7.6) | 14.0 | 690 (16.1) | 16.7 |
| 20–24 years | 1700 (10.3) | 7.2 | 1583 (28.5) | 11.7 | 1002 (18.7) | 6.0 | 1308 (30.6) | 14.8 |
| 25–29 years | 4505 (27.3) | 7.4 | 1443 (26.0) | 11.4 | 1535 (28.6) | 8.0 | 1089 (25.5) | 14.9 |
| 30–34 years | 6288 (38.2) | 6.0 | 1125 (20.2) | 13.7 | 1582 (29.5) | 6.9 | 782 (18.3) | 12.5 |
| 35+ years | 3566 (21.6) | 6.7 | 681 (12.3) | 15.6 | 839 (15.6) | 8.1 | 406 (9.5) | 17.2 |
| Trendc | p=0.02 | p=0.002 | p=0.07 | p=0.44 | ||||
|
| ||||||||
| Maternal education | ||||||||
| > 12 years | 13647 (82.8) | 6.3 | 2835 (51.2) | 10.4 | 3170 (59.5) | 6.5 | 1972 (46.3) | 12.1 |
| = 12 years | 2159 (13.1) | 8.6 | 1738 (31.4) | 13.5 | 818 (15.4) | 9.9 | 1232 (28.9) | 15.4 |
| < 12 years | 685 (4.2) | 8.3 | 970 (17.5) | 15.9 | 1337 (25.1) | 9.3 | 1054 (24.8) | 19.5 |
| Trendc | p=0.0001 | p<0.0001 | p=0.0004 | p<0.0001 | ||||
|
| ||||||||
| Marital status | ||||||||
| Married | 15072 (91.3) | 6.9 | 2501 (45.0) | 12.0 | 4191 (78.2) | 7.5 | 1593 (37.3) | 12.3 |
| Not married | 1444 (8.7) | 9.8 | 3057 (55.0) | 16.0 | 1172 (21.9) | 11.7 | 2682 (62.7) | 20.9 |
|
| ||||||||
| Tobacco use | ||||||||
| Nonsmoker | 15596 (94.5) | 6.8 | 5046 (90.9) | 12.9 | 5119 (96.2) | 8.0 | 3886 (91.3) | 16.0 |
| Smoker | 908 (5.5) | 13.8 | 508 (9.2) | 28.0 | 205 (3.9) | 18.5 | 369 (8.7) | 35.2 |
|
| ||||||||
| Prenatal care | ||||||||
| Adequate | 15623 (94.9) | 7.0 | 1359 (75.4) | 13.0 | 4929 (94.5) | 7.9 | 3457 (82.0) | 15.7 |
| Not adequate | 834 (5.1) | 10.3 | 4154 (24.7) | 17.7 | 286 (5.5) | 14.9 | 760 (18.0) | 26.0 |
|
| ||||||||
| Gravidity | ||||||||
| First pregnancy | 6070 (36.8) | 7.4 | 1566 (28.2) | 10.9 | 2233 (41.7) | 8.1 | 1309 (30.8) | 14 |
| 2–5 pregnancies | 10049 (60.9) | 6.1 | 3589 (64.6) | 12 | 3004 (56.2) | 7.4 | 2736 (64.4) | 14.9 |
| 6+ pregnancies | 389 (2.4) | 11.8 | 399 (7.2) | 21.8 | 113 (2.1) | 8.8 | 206 (4.9) | 19.4 |
| Trendc | p=0.2 | p<0.0001 | p=0.5 | p=0.1 | ||||
|
| ||||||||
| % black in maternal census tract | ||||||||
| <25 | 14450 (87.5) | 6.6 | 2521 (45.4) | 10.7 | 1945 (36.3) | 6.9 | 424 (9.9) | 11.6 |
| 25–49 | 1731 (10.5) | 7.4 | 1303 (23.4) | 14.4 | 2243 (41.8) | 7.9 | 1385 (32.4) | 12.1 |
| 50–74 | 281 (1.7) | 9.6 | 867 (15.6) | 12.0 | 873 (16.3) | 8.6 | 1115 (26.1) | 16.0 |
| 75+ | 55 (0.3) | 5.5 | 867 (15.6) | 14.6 | 304 (5.7) | 9.9 | 1351 (31.6) | 18.0 |
| Trendc | p=0.06 | p=0.005 | p=0.03 | p<0.0001 | ||||
Sample population includes singleton live births to all non-Hispanic black and white women in Wake and Durham counties between 1999 and 2001 (n=33,220), excluding births occurring to women residing in census blocks for which no population was reported in 2000 (n=928) or for which the FIPS codes did not correspond to Wake or Durham county (n=2), those with missing gestational age data (n=7), and those with impossible birth weight data (n=29); sample used in analysis consisted of 31,715 births
Missing values ranged from 0.0% (marital status among white women in Wake and Durham) to 2.9% (prenatal care among white women in Durham)
Trends were computed using ordinal values for the categories of the x variable