This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other FP Methods and New Initiatives in Family Planning, Subject name: Social & Preventive Medicine
With DMPA, the next injection may be taken latest by: 
Select and explain. 
A. 12 weeks, B. 13 weeks, C. 15 weeks, D. 17 weeks
D: 17 weeks
Answer: D: 17 weeks 
Explanation: DMPA is effective for 13 weeks. It has grace period of 4 weeks, which means that this woman can get her next injection before completed 17 weeks. If she comes later than 17 weeks, then she will be given injection but will have to use backup for next 7 days, as injections would take time to become effective.