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Table 4 Adjusted RRs for the association between pregnancy-related conditions and breast CIS and invasive breast cancer

From: Pregnancy-related factors and the risk of breast carcinoma in situand invasive breast cancer among postmenopausal women in the California Teachers Study cohort

 

Breast CIS

Invasive breast cancer

 

Observed Person-years

Cases No.

Adjusted RR (95% CI)

Observed Person-years

Cases No.

Adjusted RR (95% CI)

P for homogeneityb

Nausea or vomiting during pregnancy

       

Ever experienced

       

   No

108,269

124

Reference

111,618

620

Reference

 

   Yes

224,001

270

1.05 (0.85 to 1.30)

230,499

1,174

0.92 (0.84 to 1.02)

0.29

Number of pregnancies during which participant experienced nausea or vomitinga

       

   1

73,892

84

0.92 (0.70 to 1.22)

75,959

380

0.91 (0.80 to 1.03)

 

   2

72,819

95

1.21 (0.91 to 1.61)

75,015

387

0.94 (0.82 to 1.07

 

   3

43,520

53

0.99 (0.70 to 1.41)

44,783

238

0.94 (0.80 to 1.11)

 

   ≥ 4

33,770

38

1.16 (0.76 to 1.77)

34,742

169

0.91 (0.75 to 1.11)

 

   P trend

  

0.37

  

0.25

0.20

Ever needed treatment for nausea or vomiting during pregnancya

       

   No

184,207

220

1.04 (0.83 to 1.30)

189,367

947

0.90 (0.81 to 1.00)

0.26

   Yes, for most recent pregnancy

19,436

24

1.09 (0.70 to 1.69)

20,092

114

1.07 (0.88 to 1.31)

0.96

   Yes, for other pregnancy(ies)

20,358

26

1.14 (0.74 to 1.74)

21,039

113

1.01 (0.83 to 1.24)

0.63

Preeclampsia

       

Ever diagnosed with preeclampsia

       

   No

304,969

361

Reference

314,176

1673

Reference

 

   Yes, during most recent pregnancy

8,431

17

1.72 (1.05 to 2.81)

8,699

44

0.98 (0.73 to 1.33)

0.06

   Yes, during other pregnancy(ies)

12,379

13

0.93 (0.53 to 1.62)

12,648

51

0.77 (0.58 to 1.02)

0.57

  1. RRs for gravid postmenopausal women based on multivariable Cox proportional hazards regression models using age (in days) as the time metric and stratified by age (in years) with the adjustment for race, family history of breast cancer in a first degree relative, age at menarche, HT use, body mass index, pregnancy history (number full-term pregnancies: 1; 2; 3; ≥ 4; ever pregnant, but unknown whether full-term; ever been pregnant, but not full-term pregnancy). aCompared with gravid postmenopausal women who had never experienced nausea or vomiting during pregnancy. bHomogeneity in risk estimates between breast CIS and invasive breast cancer. Abbreviations: CIS, carcinoma in situ; RR, relative risk; CI, confidence interval; HT, hormone therapy