Safe periods are the times during your menstrual cycle when you cannot become pregnant. Generally speaking, most of the time is “safe”, while you can become pregnant during a few days of your cycle. It is specifically during the days surrounding your ovulation that you can become pregnant. If you know when that is, you can avoid becoming pregnant by choosing to have sex at times other than these days. This is what is known as safe periods.
When you ovulate, the egg travels down the fallopian tube and survives for about 24-36 hours. It is during this time that it can become fertilised.
Sperm can survive up to five days within your body, so if you have unprotected sex a few days prior to ovulation, or during your ovulation, you take the risk of becoming pregnant. The remaining time is considered a “safe” period.
How do you know when it is a safe period?
To decide on when it is a safe period is done through calculating the time from the ovulation. The unsafe time is from five days prior to ovulation until one day after ovulation. The safe periods are from the first day of menstruation until six days prior to ovulation, as well as from two days after ovulation until the next menstruation. It is a challenge to know exactly what day your ovulation occurs. Normally, it occurs within the span of a few days. This makes for a little longer unsafe period and a little shorter safe period.
If you have a 28-day menstrual cycle, you will ovulate approximately 12-16 days after the beginning of your latest menstruation. Your first day of menstruation, i.e. the day that you get your period, is called day 1. Then you will ovulate on about day 13-17.
Exmaple of a calendar marked with menstruation and ovulation days
The egg survives approximately one day, so intercourse after day 18 is safe. Since the sperms can survive up to five days, you should refrain from having sex from day 8. Thus, your safe periods are days 1-7, as well as days 19-28. This is valid if your menstrual cycles are of equal length. If your menstrual cycle varies a bit in length, you will need to adjust the days so that your safe periods become shorter. If you have a menstrual cycle which varies between 26 and 30 days, your safe periods are days 1-5, as well as day 21 until your next menstruation.
At last, some good advice. Consider that, by using safe periods as a substitute for contraceptives over a longer period of time, there is a very strong chance that you will eventually become pregnant. A small disturbance of your menstrual cycle is enough for your ovulation to occur outside the margins of the original plan, and you risk becoming pregnant.