Lymphoma is the fourth most common cancer in pregnancy, affecting one in 6000 pregnancies. Non-Hodgkin lymphoma, acute leukaemia, and other blood cancers, while also rare, can also occur in pregnancy.

The need for urgent chemotherapy and the increased risk of blood clots during pregnancy, which is enhanced in blood cancers, mean that it is advisable to terminate a pregnancy if it is in its early stages to protect the health of the mother.

However cancers discovered later in pregnancy can be treated. The issues around blood cancers in pregnancy are discussed in the third paper of The Lancet Series on pregnancy in cancer, written by Dr Benjamin Brenner, Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel, and colleagues.

The rarity of these cancers means large-scale trials of any description in pregnant women have been unfeasible, and thus much of the evidence is based on case reports or case series.

A constellation of risk factors coming together makes it advisable for pregnant women with blood cancers (who wish to continue their pregnancy) to undergo thromboprophylaxis with heparin during their pregnancy. The higher risk of clotting during pregnancy and birth is further increased by cancer-related factors and the chemotherapy agents used to treat cancer.

Thromboprophylaxis reduces the risk of deep-vein thrombosis or pulmonary embolism in the mother, and may also decrease the risk of placental thrombosis, and fetal growth restriction or death.

The authors advise that, in the absence of a durable remission of at least 2–3 years, avoidance of pregnancy is advisable in patients with acute leukaemia or lymphoma because the disease is most likely to recur during that period. Whether there is any association between pregnancy and risk of relapse remains unclear.

They add that as combined hormonal contraceptives increase the risk of thrombosis, they are not recommended in patients with active disease but they can be considered for those in long-term remission. However, progesterone-only preparations, either taken orally or as an intrauterine device, are thought to be safe.

Blood cancers in pregnancy, although rare, poses diagnostic and therapeutic challenges. Management should focus on survival of the mother, while minimising treatment-related fetal toxic effects. The authors conclude that the scarcity of data emphasises the need for extensive collaborative efforts to expand basic and clinical research in this important setting.

Source: The Lancet Oncology