Table 3.

Multivariate Cox proportional hazards analysis of rate of first birth in age groups 15-19, 20-24, and ⩾25 years at follow up. Differences in birth rate according to diagnosis at operation adjusted for year of woman’s birth and age at operation. Values are adjusted hazard ratios (95% confidence intervals); P values

Factor	15-19 years	20-24 years	⩾25 years
Diagnosis at operation:
Control	1.00	1.00	1.00
Normal appendix	2.57 (2.34 to 2.83); <0.001	1.63 (1.53 to 1.73); <0.001	1.03 (0.95 to 1.11); 0.51
Appendix not perforated	1.37 (1.24 to 1.50); <0.001	1.11 (1.06 to 1.17); <0.001	1.05 (0.99 to 1.11); 0.051
Perforated appendix	0.84 (0.63 to 1.12); 0.23	0.89 (0.78 to 1.01); 0.08	1.03 (0.92 to 1.16); 0.59
Year of woman’s birth:
Before 1960	1.00	1.00	1.00
1960-4	0.53 (0.49 to 0.57); <0.001	0.77 (0.74 to 0.81); <0.001	1.07 (1.03 to 1.11); <0.001
1965-9	0.39 (0.36 to 0.43); <0.001	0.83 (0.79 to 0.86); <0.001	0.97 (0.92 to 1.01); 0.13
After 1969	0.53 (0.47 to 0.60); <0.001	0.71 (0.66 to 0.76); <0.001	0.82 (0.66 to 1.01); 0.06
Age at operation (years):
<11	1.00	1.00	1.00
11	1.00 (0.90 to 1.11); 0.96	0.95 (0.90 to 0.99); <0.04	1.01 (0.95 to 1.06); 0.85
12	0.99 (0.89 to 1.10); 0.88	0.94 (0.89 to 0.99); <0.02	1.02 (0.97 to 1.07); 0.47
13	1.08 (0.98 to 1.19); 0.14	0.97 (0.92 to 1.02); 0.27	1.01 (0.96 to 1.06); 0.73
14	1.07 (0.97 to 1.18); 0.16	0.96 (0.91 to 1.01); 0.08	1.05 (1.00 to 1.10); <0.05