Malignancy complicates between 0.02% and 0.10% of all pregnancies and in one study cancer diagnosis was associated with 1 in 1000 deliveries. Pregnancy does not affect the frequency of cancers seen in women of childbearing age. Melanoma may be the most frequent malignancy seen during pregnancy (1:350), followed by cervical cancer (1:2250), Hodgkin lymphoma (1:3000), breast cancer (1:7500), ovarian cancer (1:18,000), and leukemia (1:75,000). However, the National Cancer Institute maintains that breast cancer is the most common cancer seen in pregnant and postpartum women at 1:3000 pregnancies (www.cancer.gov/cancertopics/pdq/treatment/breast-cancer-and-pregnancy).
In general, the prognosis for pregnant women with malignant lesions is the same, stage for stage, as for nonpregnant women. However, for many reasons, diagnosis of cancer during pregnancy occurs at more advanced stages of the disease.
Typically, during pregnancy, what benefits the mother also benefits the fetus. However, that is not true in the case of the pregnant woman with cancer as treating the cancer often means compromising the pregnancy. Depending on the type of cancer and gestational age at diagnosis, treatment can sometimes be delayed until the fetus is either viable or mature. In some cases, protection of maternal and fetal health are congruent, but when care of the mother imposes iatrogenic risk to the fetus, the mother may decide to delay or alter her treatment for the good of the fetus, potentially to her own detriment.
Fetal and uterine monitoring during cancer surgery is controversial.