Table 2. Pooled ORs and 95% CIs for the Association Between Mean Duration of Breastfeeding per Episode and Invasive Ovarian Cancer Risk Stratified by Parity in the Ovarian Cancer Association Consortium.
| Variable | Controls, No. (%) | All invasive | High-grade serous | ||
|---|---|---|---|---|---|
| Women with ovarian cancer, No. (%) | OR (95% CI) | Women with ovarian cancer, No. (%) | OR (95% CI) | ||
| Mean breastfeeding duration per episode, moa,b | |||||
| Never breastfed | 4426 (32) | 3257 (41) | 1 [Reference] | 1978 (42) | 1 [Reference] |
| 0 to <3 | 3473 (25) | 1879 (24) | 0.82 (0.76-0.88) | 1067 (23) | 0.79 (0.72-0.86) |
| 3 to <6 | 2553 (19) | 1311 (17) | 0.75 (0.69-0.82) | 776 (17) | 0.76 (0.68-0.84) |
| 6 to <9 | 1454 (11) | 676 (9) | 0.69 (0.62-0.76) | 394 (8) | 0.68 (0.60-0.78) |
| 9 to <12 | 914 (7) | 399 (5) | 0.66 (0.58-0.76) | 235 (5) | 0.68 (0.58-0.79) |
| ≥12 | 934 (7) | 400 (5) | 0.66 (0.58-0.75) | 218 (5) | 0.66 (0.56-0.78) |
| P value for trendc | NA | NA | .001 | NA | .01 |
| Mean breastfeeding duration per episode among women with 1 birth, mod | |||||
| Never breastfed | 881 (40) | 716 (47) | 1 [Reference] | 389 (50) | 1 [Reference] |
| 0 to <3 | 573 (26) | 364 (24) | 0.90 (0.75-1.07) | 188 (24) | 0.94 (0.76-1.18) |
| 3 to <6 | 316 (14) | 200 (13) | 0.85 (0.69-1.06) | 92 (12) | 0.81 (0.61-1.07) |
| 6 to <9 | 161 (7) | 93 (6) | 0.74 (0.55-0.98) | 41 (5) | 0.68 (0.46-1.00) |
| 9 to <12 | 130 (6) | 67 (4) | 0.68 (0.49-0.94) | 36 (5) | 0.78 (0.52-1.17) |
| ≥12 | 169 (8) | 88 (6) | 0.66 (0.49-0.89) | 37 (5) | 0.64 (0.43-0.95) |
| P value for trendc | NA | NA | .01 | NA | .01 |
| Mean breastfeeding duration per episode among women with 2 births, mod | |||||
| Never breastfed | 1726 (32) | 1257 (42) | 1 [Reference] | 765 (44) | 1 [Reference] |
| 0 to <3 | 1325 (24) | 700 (23) | 0.83 (0.73-0.94) | 377 (21) | 0.76 (0.65-0.88) |
| 3 to <6 | 1087 (20) | 493 (16) | 0.69 (0.60-0.79) | 279 (16) | 0.68 (0.57-0.80) |
| 6 to <9 | 611 (11) | 277 (9) | 0.67 (0.57-0.80) | 171 (10) | 0.70 (0.57-0.86) |
| 9 to <12 | 349 (6) | 131 (4) | 0.57 (0.45-0.71) | 72 (4) | 0.52 (0.39-0.68) |
| ≥12 | 372 (7) | 161 (5) | 0.67 (0.54-0.82) | 90 (5) | 0.66 (0.51-0.86) |
| P value for trendc | NA | NA | .02 | NA | .13 |
| Mean breastfeeding duration per episode among women with 3 births, mod | |||||
| Never breastfed | 1013 (29) | 750 (39) | 1 [Reference] | 470 (40) | 1 [Reference] |
| 0 to <3 | 899 (26) | 469 (24) | 0.77 (0.66-0.90) | 268 (23) | 0.72 (0.60-0.87) |
| 3 to <6 | 640 (19) | 342 (17) | 0.77 (0.65-0.91) | 226 (19) | 0.85 (0.69-1.04) |
| 6 to <9 | 408 (12) | 174 (9) | 0.66 (0.53-0.82) | 106 (9) | 0.68 (0.53-0.88) |
| 9 to <12 | 262 (8) | 118 (6) | 0.74 (0.57-0.95) | 71 (6) | 0.76 (0.56-1.03) |
| ≥12 | 220 (6) | 66 (3) | 0.51 (0.38-0.70) | 41 (3) | 0.58 (0.40-0.84) |
| P value for trendc | NA | NA | .04 | NA | .42 |
Abbreviations: NA, not applicable; OR, odds ratio.
a
Adjusted for age, race/ethnicity, oral contraceptive use, parity, birth decade, and study site.
b
Mean duration of breastfeeding per child breastfed.
c
Among women who breastfed.
d
Adjusted for age, race, oral contraceptive use, birth decade, and study site.