Dry Day Rule Courtney Updated August 29, 2017 22:15 Follow Dry Day Rule: One of the four rules of using FAM as birth control: You are considered infertile in the evening (after 6 PM) of any day that you observed no cervical fluid, and your vaginal sensation was dry. Related articles Cervical Fluid and Avoiding Pregnancy Dry Days First 5 Days Rule The 4 Rules of Charting for Birth Control Healthy Cycle Comments 2 comments Sort by Date Votes iversonkkr April 29, 2014 13:26 Why only after 6 PM? Can I have safe unprotected sex in the morning? 1 Permalink Courtney April 29, 2014 15:36 Hey there, The 6 PM rule is there to give any cervical fluid enough time to descend through the vagina throughout the day. Though unlikely, it's possible that sperm from unprotected sex in the morning could survive long enough to meet fertile cervical fluid in the afternoon. However, if you verify before having sex that there is no cervical fluid at the os (cervical opening), and that your cervix is in its most infertile position (low, firm, and closed for most women), your increased risk of pregnancy is probably very small. I say 'probably' because no studies have been done on the matter - so it's up to you whether you want to take on a slightly increased risk of pregnancy. 1 Permalink Please sign in to leave a comment.