Childbearing and mortality from cancer of the corpus uteri

BACKGROUND: To investigate the mortality from cancer of the corpus uteri in relation to parity and age at first and last birth. METHODS: A cohort of 431,604 married women aged 45-74 years at the Norwegian Census in 1970 was followed over 15 years. A total of 752 deaths from cancer of the corpus uteri were diagnosed during follow-up. RESULTS: All age groups showed significant trends of decreasing mortality rates with increasing number of children. The age-adjusted reduction in mortality was 9.2% (95% CI 5.2-13.0) for each child. Women with 8-11 children had a relative risk of 0.35 (95% CI 0.14-0.85) compared to nulliparous women. For first birth at age > = 35 years versus < = 19 years, the relative risk was 0.53 (95% CI 0.34-0.83). No significant effect of age at last birth was found. CONCLUSIONS: This study supports the notion that high parity and postponing the first delivery may reduce the risk of uterine cancer death.