Pregnancy in association with a newly diagnosed cancer: a population-based epidemiologic assessment.

Cancer patients who were pregnant at the time of cancer diagnosis were identified by the National Cancer Registry of the German Democratic Republic for the years 1970 through 1979. A total of 355 such cases occurred in women aged 15-44, and during the same period 2, 103, 112 live births were registered. Rank by site in order of decreasing frequency was cervix, breast, ovary, lymphoma, melanoma, brain and leukemia. On the basis of general female population rates, 555.8 cases were expected, giving a significantly reduced observed to expected ratio (O/E) of 0.64. O/E ratios rose with age. The O/E for invasive carcinoma of the cervix was significantly elevated at 1.15; carcinoma in situ of the cervix occurred significantly less frequently than expected (O/E = 0.57). For breast, brain, melanoma and leukemia, significantly fewer cases were observed than expected. Explanations considered for the low number of pregnancy-associated incident cancer cases include underreporting of pregnancy-associated cancer, altered tumor progression in pregnancy or decreased fertility in women with early neoplastic disease.