Malignancies may be affected by the different hormonal profile of pregnancy and its effects on the tissues; this may make certain tumours more aggressive (e.g. breast cancer, melanoma). Some maternal malignancies may metastasise to the fetus or placenta (e.g. melanoma), although in general this is rare.
The patient's medication may need altering, especially in early pregnancy, since many cytotoxic drugs are harmful to the fetus. Similarly, there may be concerns about the use of radiotherapy or even surgery to treat malignancy during pregnancy, and the risks and benefits to both the mother and the fetus of administering or withholding treatment need careful consideration. In addition, the normal psychological stresses of pregnancy and delivery are especially intense if the mother has (or has had) cancer. The physiological demands of normal pregnancy may stress the more susceptible systems in the mother with malignant disease, e.g. anaemia may become more pronounced; mild cytotoxic-induced cardiomyopathy may become more severe. Finally, there may be direct effects of the malignancy or its treatment on the uterus and birth canal, e.g. cervical surgery and scarring, perineal scarring and abdominal adhesions.
A particular form of malignant disease affecting pregnancy is that arising from the placenta itself (gestational trophoblastic neoplasia), comprising hydatiform mole, invasive mole, choriocarcinoma and placental site trophopbastic tumour. It is more common at the extremes of reproductive age, in the Far East and Asia and if previous pregnancies have been affected. The pregnancy itself is non-viable and concerns about the fetus do not apply. These tumours generally respond well to chemotherapy, even if metastatic spread has occurred, with a mortality of <1%. Molar pregnancy may be associated with hyperemesis, hypertensive disease, anaemia, ovarian cysts and rarely hyperthyroidism. Surgical evacuation may be followed by pulmonary oedema or acute lung injury, possibly related to trophoblastic pulmonary embolism.
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