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Table 4 Odds ratios (OR) with 95% confidence intervals (CI) for breast cancer associated with use of oral contraceptives (OCs) in relation to the first birth.

From: Oral contraceptive use before first birth and risk of breast cancer: a case control study

Use of OC

Cases

Controls

Crude

Adjusted*

 

n

n

OR

OR

95% CI

User after 1st birth

7

12

0.8

0.8

(0.2, 2.5)

User before 1st birth

74

143

1.1

1.0

(0.5, 1.7)

User, no births

32

62

1

1

 

Order of use and births** not known

1

5

   
  1. ‡ Women missing information about OC use or (21 cases and 37 controls) or having not used OCs while in the HSHS (15 cases and 57 controls) were excluded. *Adjusted for sports (no sports, sports, unknown) and smoking (never, ever, unknown). † Reference group. **Chronological order of the first delivery and start of OC use.