This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sexually Transmitted Disease in the Female, Subject name: Gynaecology & Obstetrics
According to Naegele's rule, calculate EDD of a patient with LMP 9/1/2017: 
Select and explain. 
A. 16/10/2017, B. 16/09/2017, C. 16/11/2017, D. 9/10/2017
A: 16/10/2017
Answer: A: 16/10/2017 
Explanation: ANS. A* Adding 7 days + 9 months to LMP gives EDD* Naegele's rule is based on 28 days regular cycle* If the cycle is shorter or longer than 28 days, EDD will be corrected and written as corrected EDD.For irregular cycles:1. If she is having 40 days cycle regularly, to get corrected EDD, add (40-28) with the EDD calculated from LMP.2. If she is having 21 days cycle regularly, to get corrected EDD, substract (28-21) 7 with the EDD calculated from LMP.