Table 3.
Adjusted relative and absolute risk of preterm birth by volume of tissue excised
| Volume of excisional treatment | No (%) cases | No (%) controls | Relative risk* (95% CI) | Absolute risk (%) |
|---|---|---|---|---|
| Punch biopsy | 210 (27.3) | 274 (33.0) | 0.97 (0.75 to 1.27) | 7.3 |
| Small volume (≤1.77 cm3) | 229 (29.8) | 297 (35.8) | 1 (reference) | 7.4 |
| Medium volume (1.78-2.65 cm3) | 95 (12.4) | 90 (10.8) | 1.40 (1.02 to 1.93) | 10.4 |
| Large volume (≥2.66 cm3) | 165 (21.5) | 98 (11.8) | 2.07 (1.56 to 2.76) | 15.4 |
| Unknown volume | 69 (9.0) | 71 (8.6) | 1.26 (0.88 to 1.79) | 9.4 |
*Adjusted for parity, index of multiple deprivation, maternal age at delivery, and study site.