Table 1.
Characteristics of case and control subjects.
| Cases (n=100) | Controls (n=158) | OR (95% CI) | |
|---|---|---|---|
| n (%) | n (%) | ||
| Maternal age, years. Mean (SD) | 31.5 (5.6) | 32.3 (4.8) | 1.0 (0.9, 1.0) |
| Gestational age, complete weeks. Mean (SD) | 33.0 (3.3) | 32.7 (3.3) | N/A* |
| Prepregnancy BMI. Mean (SD) | 25.6 (5.4) | 25.1 (5.2) | 1.0 (1.0, 1.1) |
| Race | |||
| White | 69 (69.0%) | 114 (72.2%) | 1.0 (Reference) |
| Black | 9 (9.0%) | 9 (5.7%) | 1.7 (0.6, 4.4) |
| Asian | 11 (11.0%) | 15 (9.5%) | 1.2 (0.5, 2.8) |
| Other | 11 (11.0%) | 20 (12.7%) | 0.9 (0.4, 2.0) |
| Hispanic descent | 17 (17.0%) | 14 (8.9%) | 2.1 (1.0, 4.5) |
| Annual income ($/year) | |||
| >70 K | 54 (54.0%) | 111 (70.3%) | 1.0 (Reference) |
| 50–70 K | 7 (7.0%) | 12 (7.6%) | 1.2 (0.4, 3.2) |
| 30–50 K | 9 (9.0%) | 9 (5.7%) | 2.1 (0.8, 5.5) |
| <30 K | 13 (13.0%) | 8 (5.1%) | 3.3 (1.3, 8.5) |
| Missing | 17 (17.0%) | 18 (11.4%) | 1.9 (0.9, 4.1) |
| Marital status | |||
| Married, living together | 68 (68.0%) | 137 (86.7%) | 1.0 (Reference) |
| Not married, living together | 15 (15.0%) | 15 (9.5%) | 2.0 (0.9, 4.4) |
| Not married, not living together | 10 (10.0%) | 5 (3.2%) | 4.0 (1.3, 12.3) |
| Divorced, separated or widow | 7 (7.0%) | 1 (0.6%) | 14.1 (1.7, 116.8) |
| Education | |||
| Graduate/professional school | 39 (39.0%) | 64 (40.5%) | 1.5 (0.8, 2.7) |
| College | 27 (27.0%) | 66 (41.8%) | 1.0 (Reference) |
| Some college | 16 (16.0%) | 17 (10.8%) | 2.3 (1.0, 5.2) |
| High school | 14 (14.0%) | 9 (5.7%) | 3.8 (1.5, 9.8) |
| Some high school | 4 (4.0%) | 2 (1.3%) | 4.9 (0.8, 28.3) |
| Insurance type | |||
| Private/HMO | 84 (84.0%) | 133 (84.2%) | 1.0 (Reference) |
| Medicaid/Mass Health | 16 (16.0%) | 24 (15.3%) | 1.1 (0.5, 2.1) |
| Employed | 86 (86.0%) | 126 (79.8%) | 1.6 (0.8, 3.1) |
| Anxiety disorder | 17 (17.0 %) | 11 (7.0%) | 2.7 (1.2, 6.1) |
| Depression | 18 (18.0%) | 9 (5.7%) | 3.6 (1.6, 8.4) |
| Uterine fibroids | 7 (7.0%) | 6 (3.8%) | 1.9 (0.6, 5.8) |
| Asthma | 20 (20.0%) | 19 (12.0%) | 1.8 (0.9, 3.6) |
| Primiparous | 63 (63.0%) | 94 (59.9%) | 1.1 (0.7, 1.9) |
| Previous therapeutic abortions | 19 (19.0%) | 17 (10.8%) | 1.9 (1.0, 3.9) |
| Previous miscarriages | 24 (24.0%) | 37 (23.8%) | 1.0 (0.6, 1.8) |
| Prior preterm gestation (<37 weeks) | 9 (9.0%) | 2 (1.3%) | 7.7 (1.6, 36.3) |
| Difficulties becoming pregnant (>6 months) | 31 (31.3%) | 35 (22.2%) | 1.6 (0.9, 2.8) |
| Planned pregnancy | 72 (72.0%) | 113 (71.5%) | 1.0 (0.6, 1.8) |
| Fertility treatment to become pregnant | 24 (33.3%) | 16 (14.2%) | 3.1 (1.5, 6.4) |
| In vitro fertilization (IVF) | 22 (22.0%) | 12 (7.6%) | 3.4 (1.6, 7.3) |
| Twin pregnancy | 19 (19.0%) | 4 (2.5%) | 9.0 (3.0, 27.4) |
| Vaginal bleeding/spotting in 1st trimester | 37 (37.4%) | 29 (18.4%) | 2.7 (1.5, 4.7) |
| Vaginal bleeding/spotting in 2nd trimester | 15 (15.0%) | 7 (4.4%) | 3.8 (1.5, 9.7) |
| Prescribed progesterone | 9 (9.0%) | 2 (1.3%) | 7.8 (1.6, 36.9) |
*
There was no difference between groups because participants were matched on gestational age in weeks.