Love Matters | Rita Lino

A guide to calculating your safe period

Bernadette looked down at the home pregnancy test kit she held in her hands. Two lines meant positive; she was pregnant. She was not ready to be a parent, and neither was Ayo. Even though they were in a committed relationship, they had discussed their plans and a baby did not fit into the immediate plans.

Whether you are in a relationship or not and no matter your preferred method of birth control, all information about yours and your partner’s reproductive health is important. There are no 100% foolproof methods of contraception because the body chemistry differs slightly at any given point in time. However, generally every month, there is only a short period of time, usually a window of about eight (8) to eleven (11) days right in the middle of a menstrual cycle where pregnancy may occur. The rest of the time outside of these days are considered safe.

The method of contraception described below is the Calendar Method and the primary function is to know when you are in your safe period or ovulating. ‘Safe period’ refers to the days when a woman has reduced chances of getting pregnant. To calculate your safe period, you need to first find out your fertility period. Here are the steps:

  1. Keep track of the length of your menstrual cycle for at least 6 to 8 months. A menstrual cycle is a time from the first day of one period to the day before the first day of another period. On average, a menstrual cycle is usually 28 to 30 days. However, anything between 21 to 35 days is medically acceptable. Write down the longest and shortest number of days from your monthly tracking.
  2. To calculate the first day of your fertility window, subtract 18 days from the length of your shortest cycle. For example, if your shortest cycle was 27 days, subtract 18 from 27, and write down day 9.
  3. To calculate the last day of your fertility window, subtract 11 from your length of the longest cycle. For example, if it was 30 days, you’d get day 19.
  4. On a calendar, mark day 9 from the first day of your period this month (first day inclusive) and then continue counting till you mark day 19. The time between day 9 and 19 in this example is the fertility window. This means you should avoid unprotected sex during this period. Days 1-8 and 20 onwards are generally considered safe.
  5. You may decide to take advantage of technology and use one of the apps built for the purpose of monitoring menstrual cycles like Period Calendar, My Calendar, Flo, Eve and so on.

To aid easier decision making, we have highlighted the pros and cons of calculating your safe period below:


• The method has no side effects;

• It is always available.


• Not 100% safe;

• Does not protect from sexually transmitted diseases;

• You can only have intercourse during certain periods.

Disclaimer: this method may not work with women who have regular cycles shorter than 27 days. Also, for other people, the method is only about 85% safe in a 12-month period were calculated correctly.

Do note that, sperm can live inside your uterus for up to five days after having sex. Therefore, having unprotected sex during your period or outside of your expected fertile window isn’t a guarantee that you won’t get pregnant. It is safest to combine the calendar method with other methods of contraception for a full babyproof experience.

Do you have questions about safe periods? Drop them below or reach out to our Moderators on our Facebook Page and we will respond.

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