Table 1. Weighted Characteristics of Enrolled Singleton Pregnancies and Those Included in the Placental Case-Control Analysis.
| Characteristic - weighted n (%)* | Singleton Stillbirths | Singleton Live Births | ||||
|---|---|---|---|---|---|---|
|
| ||||||
| Enrolled | Included | P† | Enrolled | Included | P† | |
|
|
|
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| Unweighted sample size | n=620 | n=518 | n=1871 | n=1200 | ||
| Weighted sample size | nw=622 | nw=518 | nw=1412 | nw=966 | ||
|
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| Maternal age at delivery, years | ||||||
| <20 | 84 (13.5) | 74 (14.3) | 0.617 | 148 (10.5) | 100 (10.3) | 0.653 |
| 20-34 | 433 (69.7) | 358 (69.2) | 1070 (75.8) | 737 (76.3) | ||
| 35-39 | 76 (12.3) | 62 (11.9) | 163 (11.5) | 106 (11.0) | ||
| 40+ | 28 ( 4.6) | 24 ( 4.6) | 30 ( 2.1) | 23 ( 2.4) | ||
| Maternal race/ethnicity | ||||||
| Non-Hispanic white | 209 (33.6) | 177 (34.2) | 0.260 | 641 (45.4) | 435 (45.0) | 0.702 |
| Non-Hispanic black | 146 (23.6) | 115 (22.2) | 168 (11.9) | 112 (11.6) | ||
| Hispanic | 227 (36.5) | 195 (37.8) | 498 (35.3) | 351 (36.4) | ||
| Other | 39 ( 6.3) | 30 ( 5.8) | 104 ( 7.4) | 68 ( 7.0) | ||
| Maternal education, grade | ||||||
| 0-11 (none/primary/some secondary) | 141 (24.6) | 116 (24.1) | 0.679 | 248 (18.6) | 167 (18.3) | 0.441 |
| 12 (completed secondary) | 171 (29.9) | 141 (29.5) | 349 (26.1) | 249 (27.2) | ||
| 13+ (college) | 261 (45.6) | 223 (46.4) | 740 (55.3) | 500 (54.6) | ||
| Marital status/cohabitating | ||||||
| Not married or cohabitating | 146 (25.3) | 124 (25.7) | 0.899 | 206 (15.4) | 143 (15.6) | 0.340 |
| Cohabitating | 150 (26.0) | 124 (25.7) | 325 (24.2) | 211 (23.0) | ||
| Married | 280 (48.7) | 234 (48.7) | 811 (60.4) | 565 (61.5) | ||
| Insurance/method of payment | ||||||
| No insurance | 38 ( 6.2) | 33 ( 6.4) | 0.8 | 51 ( 3.6) | 42 ( 4.4) | 0.143 |
| Any public/private assistance | 332 (53.7) | 274 (53.2) | 692 (49.0) | 475 (49.2) | ||
| VA/commercial health insurance/HMO | 248 (40.2) | 208 (40.4) | 668 (47.3) | 449 (46.5) | ||
| Gestational age at delivery‡ | ||||||
| 18-19 | 17 ( 2.7) | 11 ( 2.1) | 0.04 | 0 ( 0.0) | 0 ( 0.0) | 0.028 |
| 20-23 | 210 (33.8) | 164 (31.7) | 5 ( 0.3) | 3 ( 0.3) | ||
| 24-27 | 92 (14.8) | 76 (14.7) | 9 ( 0.6) | 5 ( 0.5) | ||
| 28-31 | 76 (12.3) | 66 (12.7) | 13 ( 0.9) | 7 ( 0.7) | ||
| 32-36 | 120 (19.3) | 105 (20.2) | 116 ( 8.2) | 74 ( 7.7) | ||
| 37+ | 106 (17.1) | 96 (18.6) | 1270 (89.9) | 878 (90.9) | ||
VA, Veterans Administration HMO, health maintenance organization.
Weighted n's, percentages and p-values are shown for all enrolled singletons (analysis weights) and for those included in the analysis (adequate placental exam, placenta not fragmented, and stillbirth not mummified) (placenta weights). The analysis weights take into account the study design and differential consent based on characteristics recorded on all eligible pregnancies that were screened for the study. The placenta weights include an additional multiplicative component which takes into account differential availability of an adequate placental exam based on characteristics that were recorded on enrolled pregnancies. Overall unweighted and weighted sample sizes are also provided. The overall weighted sample sizes and weighted n's for individual categories are not integers, but are shown rounded to the nearest integer. Overall sample sizes vary slightly by characteristic included in the table.
Modified independent-sample test comparing those included compared with those not included (see methods).
For gestational age groups among live births, the corresponding unweighted n's are: n=74 at 20-23 weeks, n=41 at 24-27 weeks, n=39 at 28-31 weeks, n=79 at 32-36 weeks, and n=967 at 37+ weeks.