This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Medical, surgical and gynaecological illness complicating pregnancy, Subject name: Gynaecology & Obstetrics
A 20yr old P1L1 with RhD negative pregnancy had a spontaneous vaginal delivery. Her baby is RhD positive. Anti D Ig should be administered within 
Select and explain. 
A. 72 hours, B. 7 days, C. 10 days, D. 30 days
A: 72 hours
Answer: A: 72 hours 
Explanation: * For successful immunoprohylaxis anti D Ig should be given as soon as possible after the sensitizing event but always within 72hours * If not given within 72hours, effo should still be made to give anti D Ig, as a dose given within 9 to 10 dose will offer some protection * Women who is already sensitized should not be given anti D Ig Reference: Greentop guidelines no 22