With DMPA, the next injection may be taken latest by:
High-Yield 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.