Timing of Treamtment During Gestation
The first trimester of pregnancy, from conception to the end of the 12th week, is the period of organogenesis, when most treatment is contraindicated. The second trimester is from week 13 to the end of week 26, and the third trimester is from the 27th week until delivery. A full-term pregnancy is 40 weeks in duration.
Implantation occurs in the first 2 weeks following conception. If chemotherapy is given at this time, a spontaneous abortion is likely to occur. All major organs and organ systems are formed during the second to eighth week of gestation. The developing embryo is most susceptible to teratogenic effects of antineoplastic agents at this time.
The ideal time for treatment is during the second trimester and early part of the third trimester, during which time the fetus is formed and continues to mature. A fetus is usually considered viable at 24 weeks.[1,2] At this time, survival is possible with neonatal intensive care. Each time the patient is seen, it is important to always document the last menstrual period, the expected date of delivery, and the gestational age, as it is essential to know when the fetus is viable.
It is also important to document the name and contact information of the patient’s obstetrician and/or maternal fetal medicine (MFM) specialist, and the hospital that will be used for delivery, so that the information is readily available in case of an emergency. If a patient is hospitalized between 24–40 weeks’ gestation in a facility with no obstetric or neonatal services, then there must be a plan of action in case the patient shows any signs of premature labor. If the patient is suspected to be in labor, steps should be taken to immediately transport her to a facility equipped with obstetrical care and a neonatal intensive care unit. At our center, we notify the gynecologist on call to assess the patient. If she is in labor, the gynecologist then contacts the nurse manager who coordinates patient transfer.
Figure 3: Management Protocol—Care of pregnant cancer patients at M.D. Anderson Cancer Center. EMR = electronic medical record; MD = medical doctor; MFM = maternal fetal medicine specialist; OB = obstetric; US = ultrasound.
Timing of delivery is crucial for patients receiving chemotherapy during pregnancy, and is based on response to chemotherapy. The last dose should be given before week 34–36, to allow sufficient time for the patient’s blood counts to recover prior to delivery. In spite of this timing, the newborn may also have pantocytopenia at birth, owing to the inability of the immature liver and kidneys to metabolize and eliminate the cytotoxic agents. When early delivery is chosen, the mother receives steroid injections to increase fetal lung functions and limit intracranial bleeds.
For the melanoma patient, it is recommended that the placenta be sent to pathology at the time of delivery, as melanoma can cross the placental barrier.
Breastfeeding is contraindicated if chemotherapy or hormonal therapy are given postpartum, as cytotoxic agents can be excreted in breast milk.[11,15] Post delivery, the nurse can assist the patient in obtaining follow-up appointments with her oncologists to resume therapy.