Home / Sex Relationships / Can having sex during safe period prevent unwanted pregnancy? Here's how you can calculate your safe period, when a woman can have sex without protection without risking pregnancy. Debjani Arora Updated: March 8, 2016 10:11 am.Who Cannot Use Safe Period Calculator? You cannot use this method if the average length of your menstrual cycle is less than 26 days or more than 32 days, and the variation between the shortest and longest cycles in the last six months is eight.It will help you know the unsafe days that come before and after ovulation. You can track the fertility pattern, marking the days when you are fertile and days you are not. You should do it carefully as the pattern changes from month to month.There will be a rise in temperature during ovulation. Cervical Mucus Or Ovulation Method: It involves checking the changes in the cervical mucus everyday in the first stage of menstrual cycle until you ovulate. The vaginal discharge changes when you ovulate.This calculator requires you to know your menstrual cycle changes so that you can determine the safe days to have sex. Know the safe period by entering the first day of your last period and the duration of your last menstrual cycle.It is wise to avoid having unprotected sex even during the safe period to avoid STDs as well. Image courtesy: Getty Images Published: October 31, 2014 11:54 am Updated:March 8, 2016 10:11 am. Disclaimer: m does not guarantee any specific results as a result of.We've had IVF, do we need to use contraception? What can you tell me about the contraceptive implant? Would I be better on injections or the Pill? Last updated.How Do FAMs Work? The FAMs work by alerting you on your ovulation days. Once you know your days of ovulation, you can avoid sex or use a contraceptive to keep the sperms away from the vagina.