Diagnostic work-up

All patients require a complete physical examination. Although histological diagnosis with fine needle aspiration cytology and core biopsies are safe, general anaesthesia during the first trimester carries a 1–2% risk of spontaneous abortion. Endoscopic biopsies as well as lumbar puncture and bone marrow examinations are safe. Radiological investigations should be restricted to minimize the foetal exposure to ionizing radiation. A foetal exposure dose of 1 mGy is considered safe. Box 19.1 shows various imaging procedures and uterine/foetal exposure dose. A dose of less than 100 mGy (10 cGy) is associated with less than 1% risk of foetal malformation and carcinogenesis and hence, in the event of inadvertent exposure of pregnant women to radiation, termination of pregnancy is not recommended if the foetal dose does not exceed this limit.

During the first trimester of pregnancy, radiological investigations are indicated only if absolutely necessary. Chest X-ray with lead apron is considered safe and hence can be used with ultrasound sonogram for initial evaluation. MRI without gadolinium (which crosses the placenta) can be used to rule out metastatic disease in the brain, liver and bone when indicated. Avoidance of MRI in the first trimester of pregnancy has been suggested due to the risk of foetal heating/cavitation. Abdominal X-rays, CT scans and isotope scans should be avoided during pregnancy. However, a final decision to perform these investigations is based on the risk benefit for the mother (your patient), their expected survival and the gestation of the foetus.

Principles of management

Surgery

Surgery can be performed without major risk to the patient during the first two trimesters, but with a 1–2% risk of foetal loss, small risk of low birth weight (RR 1.5–2.0) and premature delivery. Foetal harm during surgery is due to various factors including placental transfer of drugs, intraoperative complications such as hypoxia, hypotension, and long-term supine positioning of mother during surgery causing placental underperfusion.

In the third trimester surgery after foetal maturation and delayed surgery until post-partum if appropriate are the options.

Intra-abdominal surgery is more likely to interfere with pregnancy. During major abdominal and pelvic surgery, continuous monitoring of the foetus is necessary. Measures to suppress premature labour and prophylactic treatment to improve foetal lung maturity should be undertaken if the surgery carries a risk of premature labour.

Timing of delivery and breast feeding

Delivery is generally planned after weeks 32–35 (earlier in modern neonatal units with better outcome for the baby) and 3 weeks after the last chemotherapy. Breast feeding is not recommended during chemotherapy, up to 2–4 weeks after completion of chemotherapy and during hormonal treatment.

Radiotherapy

The developing embryo or foetus is extremely sensitive to ionizing radiation, which can cause foetal loss, malformations, growth retardation and defects in intelligence. Radiotherapy is therefore contraindicated for abdominal and pelvic malignancies during pregnancy. Several studies support the use of radiotherapy for head and neck cancer, breast cancer and brain tumours. Radical radiotherapy to the head and neck and brain can be achieved with a foetal dose of less than 100 mGy (Box 19.2). During radiotherapy to the breast and chest wall, the dose to the foetus increases with gestational age. The foetal dose depends on the radiation field, dose, the distance between the edge of radiation field and foetus, and the machine and its shielding measures.