Table 1. Demographics of women in study: high risk controls and cases (women who developed a short cervix before 24 weeks' gestation) providing cervico-vaginal swabs for serial trappin2/elafin measurements throughout gestation.
| Characteristic | Sub category | Controls (n = 38) | Cases (n = 36) |
| Maternal age in years median (quartiles) | 30.0 (22.4,35) | 29.5 (27,34) | |
| BMI in (kg/m2) at booking median (quartiles) | 27.7 (23,32) | 25.1 (23,28.6) | |
| Risk Factors (N%) | previous PTB (24–34 weeks) | 20 (53) | 11 (31) |
| previous PPROM | 21 (55) | 20 (56 | |
| previous 2nd trimester loss (16–24 weeks) | 20 (53) | 29 (81) | |
| Current smoker N (%) | 3 (8) | 2 (6) | |
| Ethnic group N (%) | White | 12 (32) | 4 (11) |
| Black | 23 (60) | 30 (83) | |
| Other | 3 (8) | 2 (6) |