Recent childbirth is an adverse prognostic factor in breast cancer and melanoma, but not in Hodgkin lymphoma.

BACKGROUND: The relationship between gestation, childbirth and cancer prognosis is unknown for most cancers (e.g. Hodgkin lymphoma), whereas a body of evidence exists for melanoma and breast cancer.

METHODS: The national cancer registration and hospital discharge data for women in England (1998-2007) were linked, and the records for Hodgkin lymphoma, melanoma and breast cancer were indexed as to whether women had delivered a child in separate time periods prior to their cancer diagnosis. Survival analyses were conducted in order to characterise prognosis in relation to childbirth, with statistical adjustment for age and (where possible) stage.

FINDINGS: For melanoma and breast cancer, survival was strongly reduced in women who gave birth in the year prior to cancer diagnosis. The age-adjusted hazard ratios (HR) with 95% confidence intervals (CI) were 2.06 (1.42-3.01) for melanoma and 1.84 (1.64-2.06) for breast cancer. The associations were only slightly attenuated by further adjustment for tumour stage. For breast cancer, the excess death rate in women with a recent childbirth peaked at 2years and remained elevated for 6 to 8years. Previous childbirth had no overall effect on the outcome of Hodgkin lymphoma.

INTERPRETATION: Melanoma and breast cancer prognosis are adversely affected by recent gestation and childbirth in a way that is not due to stage of the cancer, but rather to inherent biological properties of the tumours. Possible biological mechanisms include immunosuppression (melanoma), the hormonal milieu in gestation and a tumour promoting microenvironment post-partum (breast cancer).