Table 3.
Evaluation of the multiplicative relationship between ovarian cancer and incomplete and complete pregnancies
| No. of complete pregnancies | No. of incomplete pregnancies | Expected modela | Observed modelb | Difference |
|---|---|---|---|---|
| ORjoint(expected) | ORjoint(observed) (95% CI) | ORjoint(expected) - ORjoint(observed) | ||
| 0 | 0 | 1.00 | 1.0 | |
| 1 | 0.86 | 0.84 (0.72 to 0.99) | 0.02 | |
| ≥2 | 0.80 | 0.69 (0.57 to 0.83) | 0.11 | |
| 1 | 0 | 0.75 | 0.76 (0.67 to 0.85) | −0.01 |
| 1 | 0.65 | 0.63 (0.54 to 0.75) | 0.02 | |
| ≥2 | 0.60 | 0.55 (0.46 to 0.67) | 0.05 | |
| 2 | 0 | 0.59 | 0.59 (0.53 to 0.65) | 0.00 |
| 1 | 0.51 | 0.47 (0.41 to 0.53) | 0.04 | |
| ≥2 | 0.47 | 0.51 (0.44 to 0.60) | −0.04 | |
| ≥3 | 0 | 0.51 | 0.49 (0.44 to 0.54) | 0.02 |
| 1 | 0.44 | 0.47 (0.41 to 0.57) | −0.03 | |
| ≥2 | 0.41 | 0.42 (0.36 to 0.49) | −0.01 |
a
Expected model calculated as ORcomplete* ORincomplete, using OR estimates from Table 2 and assuming multiplicativity, eg, expected OR for 2 complete and 1 incomplete = 0.59 * 0.86 = 0.51. CI = confidence interval; OR = odds ratio.
b
Observed model included a single variable with all combinations of incomplete and complete pregnancy categories (total 12 categories).