Table 3.
Retrospective, prospective, and combined analyses for the BRCA1 mutation carriers
| Characteristic | Retrospective | Ptrend* | Prospective | Ptrend* | Combined | Ptrend* |
|---|---|---|---|---|---|---|
| HR (95% CI) | HR (95% CI) | HR (95% CI) | ||||
| Parous (at least 1 full-term pregnancy)† | ||||||
| No | Referent | Referent | Referent | |||
| Yes | 0.87 (0.72 to 1.05) | 1.41 (0.94 to 2.10) | 0.99 (0.83 to 1.18) | |||
| No. of full-term pregnancy† (FTP) | ||||||
| Nulliparous (no FTP) | Referent | Referent | Reference | |||
| 1 | 0.98 (0.81 to 1.20) | <.0001 | 1.69 (1.09 to 2.62) | <.0001 | 1.11 (0.92 to 1.34) | <.0001 |
| 2 | 0.77 (0.63 to 0.95) | 1.25 (0.81 to 1.95) | 0.88 (0.73 to 1.07) | |||
| 3 | 0.68 (0.53 to 0.86) | 1.15 (0.70 to 1.90) | 0.77 (0.62 to 0.97) | |||
| ≥4 | 0.54 (0.40 to 0.73) | 0.52 (0.27 to 1.02) | 0.56 (0.42 to 0.74) | |||
| 1 | Referent | Referent | <.0001 | Reference | <.0001 | |
| 2 | 0.78 (0.68 to 0.91) | <.0001 | 0.74 (0.51 to 1.08) | 0.79 (0.69 to 0.91) | ||
| 3 | 0.69 (0.58 to 0.82) | 0.68 (0.44 to 1.05) | 0.70 (0.59 to 0.82) | |||
| ≥4 | 0.55 (0.43 to 0.70) | 0.31 (0.17 to 0.57) | 0.50 (0.40 to 0.63) | |||
| Nulliparous | 1.02 (0.83 to 1.24) | 0.59 (0.38 to 0.92) | 0.90 (0.75 to 1.09) | |||
| No. of full-term pregnancy by attained age† | ||||||
| <40 years | ||||||
| 1 | Referent | Referent | .22 | Reference | <.0001 | |
| 2 | 0.73 (0.61 to 0.87) | <.0001 | 1.08 (0.61 to 1.91) | 0.79 (0.66 to 0.94) | ||
| 3 | 0.68 (0.55 to 0.85) | 0.35 (0.12 to 1.09) | 0.65 (0.52 to 0.82) | |||
| ≥4 | 0.63 (0.45 to 0.87) | 0.67 (0.20 to 2.27) | 0.64 (0.46 to 0.89) | |||
| ≥40 years | ||||||
| 1 | Referent | <.0001 | Referent | <.0001 | Reference | <.0001 |
| 2 | 0.82 (0.66 to 1.03) | 0.61 (0.38 to 0.99) | 0.78 (0.64 to 0.96) | |||
| 3 | 0.68 (0.54 to 0.87) | 0.69 (0.41 to 1.16) | 0.70 (0.56 to 0.88) | |||
| ≥4 | 0.52 (0.39 to 0.70) | 0.24 (0.12 to 0.48) | 0.46 (0.34 to 0.61) | |||
| Age at 1st full-term pregnancy, y‡ | ||||||
| <20 | Referent | .03 | Referent | .95 | Reference | .06 |
| 20–24 | 0.98 (0.81 to 1.19) | 0.84 (0.54 to 1.30) | 0.95 (0.80 to 1.13) | |||
| 25–29 | 0.87 (0.71 to 1.06) | 0.80 (0.52 to 1.23) | 0.85 (0.71 to 1.02) | |||
| ≥30 | 0.82 (0.65 to 1.04) | 0.95 (0.59 to 1.55) | 0.86 (0.70 to 1.07) | |||
| Year since last full-term pregnancy§ | ||||||
| 0–5 | Referent | .02 | Referent | .002 | Reference | .0002 |
| 6–20 | 1.19 (1.03 to 1.36) | 0.89 (0.59 to 1.35) | 1.14 (0.99 to 1.30) | |||
| ≥21 | 1.48 (1.17 to 1.87) | 1.12 (0.63 to 1.98) | 1.44 (1.15 to 1.81) | |||
| Nulliparous | 1.05 (0.86 to 1.29) | 0.55 (0.33 to 0.89) | 0.92 (0.76 to 1.11) | |||
| Nulliparous | Referent | Referent | Reference | |||
| 0–5 | 0.95 (0.78 to 1.16) | .02 | 1.84 (1.13 to 2.99) | .002 | 1.09 (0.90 to 1.32) | .0002 |
| 6–20 | 1.13 (0.90 to 1.41) | 1.64 (1.02 to 2.64) | 1.24 (1.01 to 1.52) | |||
| ≥21 | 1.41 (1.06 to 1.87) | 2.06 (1.12 to 3.79) | 1.57 (1.20 to 2.06) | |||
| Year since last full-term pregnancy by number of full-term pregnancy† | ||||||
| 1 FTP, 0–5 | Referent | Referent | Reference | |||
| ≥2 FTP, 0–5 | 0.65 (0.53 to 0.80) | 0.75 (0.38 to 1.47) | 0.68 (0.55 to 0.84) | |||
| 1 FTP, 6–20 | 0.94 (0.73 to 1.20) | 0.96 (0.47 to 1.95) | 0.95 (0.75 to 1.21) | |||
| ≥2 FTP, 6–20 | 0.84 (0.67 to 1.04) | 0.65 (0.33 to 1.30) | 0.82 (0.66 to 1.03) | |||
| 1 FTP, ≥21 | 1.55 (1.09 to 2.21) | 1.22 (0.48 to 3.07) | 1.55 (1.11 to 2.17) | |||
| ≥2 FTP, ≥21 | 0.96 (0.72 to 1.30) | 0.81 (0.36 to 1.84) | 0.98 (0.73 to 1.31) | |||
| Breastfeeding duration‖ | ||||||
| None | Referent | .0002 | Referent | .28 | Reference | .0003 |
| 1–5 mo | 0.96 (0.82 to 1.12) | 1.07 (0.73 to 1.56) | 0.97 (0.84 to 1.11) | |||
| 6–12 mo | 0.81 (0.69 to 0.95) | 1.04 (0.70 to 1.54) | 0.84 (0.72 to 0.97) | |||
| 13–24 mo | 0.75 (0.61 to 0.91) | 1.05 (0.68 to 1.63) | 0.80 (0.67 to 0.95) | |||
| > 24 mo | 0.64 (0.48 to 0.86) | 0.75 (0.44 to 1.31) | 0.66 (0.50 to 0.87) | |||
| No. of full-term pregnancy and breastfeeding† | ||||||
| Nulliparous | Referent | Referent | Reference | |||
| 1 FTP, never breastfeeding | 1.15 (0.89 to 1.49) | 2.01 (1.14 to 3.55) | 1.33 (1.04 to 1.70) | |||
| ≥2 FTP, never breastfeeding | 0.85 (0.67 to 1.07) | 1.15 (0.67 to 1.96) | 0.94 (0.76 to 1.18) | |||
| 1 FTP, ever breastfeeding | 0.97 (0.78 to 1.19) | 1.64 (1.00 to 2.70) | 1.09 (0.89 to 1.33) | |||
| ≥2 FTP, ever breastfeeding | 0.73 (0.59 to 0.89) | 1.22 (0.79 to 1.90) | 0.84 (0.69 to 1.02) | |||
| Incomplete pregnancy§ (IP) | ||||||
| No full-term or incomplete pregnancy | Referent | Referent | Reference | |||
| Full-term pregnancy, no IP | 0.96 (0.79 to 1.16) | 1.64 (1.03 to 2.61) | 1.08 (0.90 to 1.29) | |||
| Induced abortion only | 1.02 (0.82 to 1.27) | 1.72 (1.04 to 2.83) | 1.15 (0.93 to 1.41) | |||
| Miscarriage only | 0.97 (0.78 to 1.21) | 1.77 (1.09 to 2.87) | 1.11 (0.91 to 1.36) | |||
| Induced abortion and miscarriage | 1.09 (0.77 to 1.55) | 1.09 (0.40 to 2.94) | 1.11 (0.80 to 1.55) | |||
| Incomplete pregnancy relative to first full-term pregnancy§ | ||||||
| No IP | Referent | Referent | Reference | |||
| Before first FTP or no FTP | 1.05 (0.90 to 1.22) | 1.02 (0.74 to 1.41) | 1.04 (0.91 to 1.19) | |||
| After first FTP | 1.03 (0.89 to 1.20) | 1.32 (0.93 to 1.88) | 1.09 (0.94 to 1.25) | |||
*
Nulliparous excluded, risk factor as continuous.
†
Adjusted for bilateral oophorectomy (Yes, No), age at 1st full-term pregnancy (<30, ≥30+nulliparous), strata by birth year and study site.
‡
Adjusted for bilateral oophorectomy, number of full-term pregnancies (0–1, ≥2), strata by birth year and study site.
§
Adjusted for bilateral oophorectomy, number of full-term pregnancies (0–1, ≥2), age at 1st full-term pregnancy, strata by birth year and study site.
‖
Adjusted for bilateral oophorectomy, number of live births (0–1, ≥2), age at 1st full-term pregnancy, strata by birth year and study site.