My wife periods cycle is little different each month with a slight variation and sometimes it is 7 to 15 difference, she is having pcod. Her period in December it is 4, Jan 2018 was on 3rd and in February it is 18. My question here is for March how do we calculate her cycle length? Hence it was delayed for 15 days should we consider 44 days cycle length? Which are her most fertile and ovulate days in March? She has tested her ovulation on her 13 day use the ovulation strip and the test was positive and it was just started. Please suggest.