When discussing the possibilities of fertility protection after cytotoxic therapy, the risks of a tumor relapse caused by pregnancy should also be critically evaluated. However, such an evaluation has severe limitations since experience in this field is based on a few studies with a small number of cases.

In a major Japanese study, 50 patients were documented who became pregnant in the first remission phase after acute leukaemia (Kawamura et al., Int J Hematol, 1998, 67:37-43). No increased risk of pregnancy complications or leukaemia relapse was found.

Out of 44 patients with a borderline ovarian tumor, 14 became pregnant an average of 37 months after the first diagnosis (Morice et al., Fertil Steril, 2001, 75: 92-96). In 76% of the patients, the tumor was limited to the ovaries (stage I). None of the patients had a relapse after the pregnancy.

The data situation regarding the frequency of relapse after breast cancer therapy and subsequent pregnancy is slightly better.  According to several studies, around 5% of the women with previous breast cancer carry a pregnancy to term. Theoretically, because of the hormone-dependency of breast cancer, the prognosis of the patient should get worse after a pregnancy. In several studies covering more than 700 post-delivery patients with previous breast cancer, however, no worsening of the prognosis was found (Kroman et al., Lancet, 1997, 350:319-22). When interpreting these encouraging figures, however, we should bear in mind that no detailed analysis of women with hormone-receptor-positive tumor tissue is available and that a relapse has a different ethical dimension for young mothers even if it does not seem to hit pregnant women more frequently.