Reproductive history, as measured by parity, age at first birth and sex of offspring, and cancer-specific survival after a haematological malignancy

Background Overall, women have better cancer-specific survival than men following haematological malignancies. The effect of reproductive factors on prognosis in women remains unknown and population-based studies are needed. Material and methods A nationwide cohort of 21,237 Swedish women with a recorded haematological malignancy at ages 18-69 years was identified in the Swedish Cancer Register 1970-2018. Pre-diagnosis childbirths for each woman were linked to the Swedish Multigeneration Register. Net survival and excess hazard ratios for parity, age at first birth, time since the latest birth, and sex of offspring were estimated using flexible parametric models adjusted for age, year, and educational level. Results In unadjusted analyses, parity (p = 0.0012) and high age at first birth (p < 0.0001) were associated with better survival. After co-adjustments for reproductive factors and confounders, the associations were attenuated. The adjusted association with parity was mainly observed among women aged above 40 years at diagnosis (p = 0.0033). The associations with reproductive factors were non-significant across subtypes of haematological malignancy. There was a tendency of higher excess mortality for an increasing number of boys compared to girls, although only significant for women with three or more children (p = 0.0126). Conclusion Reproductive factors were in part associated with survival following diagnosis of a haematological malignancy. However, the effect sizes were small with inconsistent association patterns, and thus reproductive factors may only partly contribute to the survival advantage of women over men.