Final answer:
Prophylactic methotrexate (MTX) is given to patients at high risk of post-molar trophoblastic neoplasia following a molar pregnancy, with indications based on beta-human chorionic gonadotropin levels and risk factors.
Step-by-step explanation:
Prophylactic administration of methotrexate (MTX) following a molar pregnancy is recommended for patients at high risk of developing post-molar trophoblastic neoplasia. A molar pregnancy is a type of gestational trophoblastic disease that can lead to persistent trophoblastic tissue and requires careful monitoring after evacuation. MTX therapy is considered when there is a rise or plateau in beta-human chorionic gonadotropin (β-hCG) levels post-evacuation, which indicates malignant transformation or presence of persistent trophoblastic tissue. MTX, an antimetabolite and folic acid antagonist, is used to treat the remaining trophoblastic cells due to its effectiveness in inhibiting DNA synthesis and cell reproduction. Prophylactic treatment is individualized and decided based on risk factors such as the level of β-hCG, age of the patient, type of molar pregnancy (complete or partial), and size of the uterus.