Table 4.

Associations of reproductive factors with ovarian cancer risk by tumor dominance.

HR (95% CI)a
Risk factorsDominantNondominantP-hetb
Parity
 Nulliparous1.00 (ref)1.00 (ref)
 1 child0.78 (0.61–1.02)0.80 (0.48–1.34)
 2 children0.60 (0.48–0.74)0.83 (0.56–1.24)
 3 children0.53 (0.43–0.67)0.92 (0.61–1.37)
 ≥4 children0.44 (0.34–0.55)0.80 (0.52–1.21)
 Per 1 child0.85 (0.81–0.89)0.97 (0.90–1.04)0.004
Tubal ligation
 No1.00 (ref)1.00 (ref)
 Yes0.74 (0.56–0.99)1.13 (0.80–1.60)0.07
Hysterectomyc
 No1.00 (ref)1.00 (ref)
 Yes0.76 (0.60–0.95)0.80 (0.58–1.10)0.79
Endometriosis
 No1.00 (ref)1.00 (ref)
 Yes1.74 (1.00–3.00)1.12 (0.40–3.15)0.45
Age at menarche (years)
 ≤111.00 (ref)1.00 (ref)
 120.90 (0.72–1.13)0.94 (0.67–1.31)
 130.95 (0.76–1.18)0.98 (0.71–1.35)
 141.06 (0.83–1.35)0.84 (0.56–1.27)
 ≥150.92 (0.71–1.20)0.85 (0.55–1.32)
 Per 1 year1.00 (0.96–1.05)0.98 (0.91–1.05)0.58
Age at menopause (years)
 ≤400.72 (0.40–1.31)0.20 (0.03–1.50)
 >40–450.77 (0.55–1.10)0.70 (0.39–1.27)
 >45–500.95 (0.76–1.18)0.93 (0.66–1.32)
 >50–551.00 (ref)1.00 (ref)
 >551.21 (0.80–1.83)0.99 (0.49–1.97)
 Per 5 years1.15 (1.03–1.30)1.22 (0.99–1.48)0.68
Age at first birth (years)
 <201.08 (0.75–1.57)0.74 (0.38–1.44)
 20–<251.00 (ref)1.00 (ref)
 25–<301.18 (0.98–1.43)0.69 (0.52–0.92)
 ≥300.93 (0.71–1.21)0.72 (0.48–1.09)
 Per 1 year1.00 (0.98–1.02)0.98 (0.95–1.01)0.28
Age at last birth (years)
 <250.98 (0.61–1.59)0.72 (0.36–1.42)
 25–<301.00 (ref)1.00 (ref)
 30–<351.02 (0.76–1.38)0.85 (0.59–1.23)
 ≥350.81 (0.55–1.19)1.18 (0.77–1.81)
 Per 1 year0.98 (0.95–1.01)1.02 (0.98–1.05)0.11
Years since last birth
 Per 1-year1.02 (0.99–1.05)0.98 (0.95–1.02)0.09
Breastfeeding
 Per 1-year0.95 (0.81–1.11)1.06 (0.89–1.26)0.32
  • aStratified by cohort and adjusted for age, parity, and duration of oral contraceptive use.

  • bPheterogeneity comparing HRs for all dominant tumors versus nondominant tumors.

  • cAdditionally adjusted for HT use.