This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Follow up of Low-risk GTN is done for 
Select and explain. 
A. 3 months, B. 6 months, C. 12 months, D. 24 months
C: 12 months
Answer: C: 12 months 
Explanation: For a molar pregnancy, post-evacuation surveillance is done at least for 6 months once b-hCG level becomes normalLow-risk GTNWeekly measurement of hCG levels until they are normal for 3 consecutive weeksMonthly measurement of hCG values until levels are normal for 12 consecutive monthsHigh-Risk Metastatic GTNWeekly determination of hCG levels until they are normal for 3 consecutive weeksMonthly determination of hCG levels until they are normal for 24 consecutive monthsThese patients require prolonged follow-up because they are at increased risk of late recurrenceReference: William's Obstetrics; 25th edition, chapter 20; Gestational trophoblastic diseases