Table 4.

Multivariate Cox proportional hazards analysis of rate first birth in patients operated on in four periods between 1964 and 1984. Values are adjusted^* hazard ratios (95% confidence intervals); P values

Factor	1964-8	1969-73	1974-8	1979-84
Diagnosis at operation:
Control	1.00	1.00	1.00	1.00
Normal appendix	1.33 (1.18 to 1.50); <0.001	1.34 (1.22 to 1.46); <0.001	1.46 (1.36 to 1.57); <0.001	1.72 (1.59 to 1.86); <0.001
Appendix not perforated	1.13 (1.03 to 1.24); <0.008	1.07 (0.99 to 1.15); 0.083	1.08 (1.02 to 1.15); <0.006	1.17 (1.10 to 1.24); <0.001
Perforated appendix	0.95 (0.75 to 1.19); 0.650	1.04 (0.87 to 1.25); 0.656	0.95 (0.82 to 1.09); 0.447	0.89 (0.76 to 1.05); 0.165
Year of woman’s birth:
Before 1960	1.16 (1.06 to 1.28); <0.001	1.12 (1.22 to 1.46); <0.001	1.07 (0.95 to 1.21); 0.234	—
1960-4	1.00	1.00	1.00	1.00
1965-9	—	1.04 (0.92 to 1.18); 0.528	0.97 (0.93 to 1.01); 0.143	0.88 (0.79 to 0.97); <0.02
After 1969	—	—	0.77 (0.57 to 1.02); 0.072	0.81 (0.73 to 0.91); <0.001

^*Adjusted for year of woman’s birth.