Table 2. HRs and 95% CIs for the association between GDM and breast cancer.
|
Ever having GDM pregnancy |
Cumulative number of GDM pregnancy |
|||||
|---|---|---|---|---|---|---|
| No GDM | GDM | 0 | 1 | ⩾2 | P-trend | |
| Person-years | 279 284 | 11 866 | 279 284 | 9355 | 2511 | |
| Total breast cancer | ||||||
| No. of cases | 2051 | 90 | 2051 | 61 | 29 | |
| HR (95% CI)a | 1 (ref) | 1.10 (0.88–1.36) | 1 (ref) | 0.94 (0.73–1.22) | 1.68 (1.15–2.44) | 0.10 |
| In situ breast cancer | ||||||
| No. of cases | 495 | 17 | 495 | 10 | 7 | |
| HR (95% CI)a | 1 (ref) | 0.78 (0.48–1.30) | 1 (ref) | 0.62 (0.33–1.17) | 1.38 (0.62–3.10) | 0.66 |
| Invasive breast cancer | ||||||
| No. of cases | 1540 | 69 | 1540 | 48 | 21 | |
| HR (95% CI)a | 1 (ref) | 1.16 (0.91–1.49) | 1 (ref) | 1.02 (0.76–1.36) | 1.72 (1.11–2.65) | 0.06 |
| ER+ invasive breast cancer | ||||||
| No. of cases | 1149 | 45 | 1149 | 29 | 16 | |
| HR (95% CI)a | 1 (ref) | 1.03 (0.76–1.40) | 1 (ref) | 0.83 (0.57–1.20) | 1.81 (1.10–2.98) | 0.31 |
| ER− invasive breast cancer | ||||||
| No. of cases | 200 | 13 | 200 | 11 | 2 | |
| HR (95% CI)a | 1 (ref) | 1.73 (0.98–3.06)b | 1 (ref) | 1.88 (1.02–3.47)b | NA | 0.12 |
Abbreviations: BMI=body mass index; CI=confidence interval; ER=oestrogen receptor; GDM=gestational diabetes mellitus; HR=hazard ratio; += positive; −=negative.
Adjusted for birth cohort (born in <1945, 1945 to <1955, 1955 to <1965 or ⩾1965), race or ethnicity (non-Hispanic white, non-Hispanic black, Hispanic and others), educational attainment (<high school, high school equivalent, some college or ⩾4-year degree), age at first birth (<21, 21 to <25, 25 to <29, 29 to <32 or ⩾32 years), age at menarche, relative weight at age 10 (lighter, same, heavier), BMI at 30–39 years old (<18.5, 18.5 to <25, 25 to <30, 30 to <35, 35 to <40 or ⩾40 kg m−2) and physical activity (quintiles of metabolic equivalent hours/week) in their childhood and teens.
HR was significantly different from ER+ breast cancer in case-only analysis.