Cause-specific survival for women diagnosed with cancer during pregnancy or lactation: a registry-based cohort study

To assess if cancers diagnosed during pregnancy or lactation are associated with increased risk of cause-specific death.

In this population-based cohort study using data from the Cancer Registry and the Medical Birth Registry of Norway, 42,511 women, age 16 to 49 years and diagnosed with cancer from 1967 to 2002, were eligible. They were grouped as not pregnant (reference), pregnant, or lactating at diagnosis. Cause-specific survival for all sites combined, and for the most frequent malignancies, was investigated using a Cox proportional hazards model. An additional analysis with time-dependent covariates was performed for comparison of women with and without a postcancer pregnancy. The multivariate analyses were adjusted for age at diagnosis, extent of disease, and diagnostic periods.

For all sites combined, no intergroup differences in cause-specific death were seen, with hazard ratio (HR) of 1.03 (95% CI, 0.86 to 1.22) and HR 1.02 (95% CI, 0.86 to 1.22) for the pregnant and lactating groups, respectively. Patients with breast (HR, 1.95; 95% CI, 1.36 to 2.78) and ovarian cancer (HR, 2.23; 95% CI, 1.05 to 4.73) diagnosed during lactation had an increased risk of cause-specific death. Diagnosis of malignant melanoma during pregnancy slightly increased this risk. For all sites combined, the risk of cause-specific death was significantly decreased for women who had postcancer pregnancies.

In general, the diagnosis of most cancer types during pregnancy or lactation does not increase the risk of cause-specific death. Breast and ovarian cancer diagnosed during lactation represents an exception. We confirmed the "healthy mother effect" for women with a postcancer pregnancy.