Table 1 Frequencies of maternal characteristics by case−control status
From: The association between gestational weight gain z-score and stillbirth: a case-control study
|  | Stillbirths (n = 479) | Live births (n = 1601) | ||
|---|---|---|---|---|
n | Weighted % | n | Weighted % | |
Plurality | ||||
 Singleton | 470 | 98.2 | 1544 | 96.7 |
 Twin (dichorionic/diamniotic) | 9 | 1.8 | 57 | 3.3 |
Maternal age at delivery, years | ||||
 < 20 | 61 | 13.2 | 193 | 10.5 |
 20–34 | 341 | 69.6 | 1194 | 75.1 |
 35–39 | 59 | 13.0 | 186 | 12.5 |
 ≥40 | 18 | 4.2 | 28 | 1.9 |
Maternal race and ethnicity | ||||
 White, non − Hispanic | 184 | 36.0 | 596 | 45.3 |
 Black, non − Hispanic | 82 | 18.4 | 268 | 10.5 |
 Hispanic | 176 | 38.5 | 620 | 35.7 |
 Other | 37 | 7.1 | 117 | 8.5 |
Study site | ||||
 State of Rhode Island and Bristol County, Massachusetts | 86 | 16.8 | 311 | 25.4 |
 DeKalb County, Georgia | 73 | 15.4 | 288 | 12.6 |
 Galveston County and Brazoria County, Texas | 49 | 9.3 | 134 | 9.0 |
 Bexar County, Texas | 143 | 35.3 | 506 | 30.2 |
 Salt Lake County, Utah | 128 | 23.2 | 362 | 22.8 |
Maternal education, grade | ||||
 0–11 (none/primary/some secondary) | 110 | 23.1 | 330 | 18.2 |
 ≥12 (completed secondary) | 369 | 77.0 | 1271 | 81.8 |
Marital status/cohabitating | ||||
 Not married or cohabitating | 110 | 24.0 | 273 | 14.1 |
 Cohabitating or married | 369 | 76.0 | 1328 | 85.9 |
Health insurance/method of payment | ||||
 Received any public/private assistance or did not have insurance | 275 | 58.9 | 923 | 52.2 |
 VA/commercial health insurance/HMOa | 204 | 41.2 | 678 | 47.9 |
Trimester prenatal care began | ||||
 First | 325 | 67.1 | 1077 | 72.2 |
 Second | 110 | 23.0 | 407 | 22.2 |
 Third or no prenatal care | 44 | 10.0 | 117 | 5.7 |
Family income in the last 12 months | ||||
 Received public/private assistance | 206 | 44.2 | 751 | 42.8 |
 Only personal income | 273 | 55.8 | 850 | 57.2 |
WIC enrollmentb | ||||
 Yes | 161 | 34.4 | 620 | 35.7 |
 No | 318 | 65.6 | 981 | 64.3 |
Used alcohol or smoked during the 3 months prior to pregnancy | ||||
 Yes | 220 | 45.7 | 696 | 47.1 |
 No | 259 | 54.3 | 905 | 52.9 |
Lifetime drug use | ||||
 Ever | 161 | 33.1 | 470 | 30.5 |
 Never | 318 | 66.9 | 1131 | 69.5 |
Pregnancy history | ||||
 Primiparous | 224 | 46.3 | 564 | 34.5 |
 Multiparous with no previous stillbirth | 223 | 46.7 | 996 | 64.1 |
 Multiparous with previous stillbirth | 32 | 7.1 | 41 | 1.4 |
Pre − pregnancy Body Mass Index | ||||
 Underweight (BMI < 18.5 kg/m2) | 18 | 3.5 | 51 | 3.1 |
 Normal weight (BMI 18.5 − < 25.0 kg/m2) | 185 | 38.3 | 760 | 49.8 |
 Overweight (BMI 25.0 − < 30.0 kg/m2) | 119 | 24.9 | 393 | 23.3 |
 Class 1 obese (BMI 30.0 − < 35.0 kg/m2) | 79 | 16.9 | 211 | 12.7 |
 Classes 2–3 obese (BMI ≥35.0  kg/m2) | 78 | 16.4 | 186 | 11.1 |
Clinical history of hypertension | ||||
 Yes | 43 | 9.4 | 113 | 6.6 |
 No | 436 | 90.6 | 1488 | 93.4 |
Clinical history of diabetes | ||||
 Yes | 26 | 5.6 | 37 | 1.7 |
 No | 453 | 94.4 | 1564 | 98.3 |
Clinical history of thyroid disorder | ||||
 Yes | 19 | 3.7 | 59 | 3.4 |
 No | 460 | 96.3 | 1542 | 96.6 |
Gestational age at delivery, weeks | ||||
 20–23 | 135 | 28.9 | 95 | 0.6 |
 24–27 | 86 | 17.8 | 87 | 0.6 |
 28–31 | 65 | 12.5 | 78 | 1.0 |
 32–36 | 98 | 21.3 | 129 | 8.6 |
 ≥37 | 95 | 19.6 | 1212 | 89.2 |