How to calculate safe period to avoid pregnancy?

Posted on April 23, 2020

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There are several birth control measures you can follow, it is imperative to make your safe days calculation in order to avoid an unwanted pregnancy.

Dr Didi tells you how to calculate safe days to prevent pregnancy, the various methods involved in it and more.

A menstrual cycle is calculated from the first day of your period to the first day of the next period. Safe period is from day 1 to 7 and day 21 to the rest of the cycle, when you can have sex without worrying about getting pregnant. This period will not be the same for all women as it depends on the length of the menstrual cycle. The average menstrual cycle is 28 days or a little less, but if your cycle is longer than 28 days, the safe period is not reliable.

It is important to have an understanding of the three stages of the menstrual cycle to avoid pregnancy.

The length of the three phases of menstrual cycle differ from one woman to the other and also from cycle to cycle, but the average duration would be 28 days .

The pre-ovulatory or the follicular phase:

It occurs in between the days 2 and 14 when your body releases hormones that stimulate the eggs in the ovaries to grow. The hormones will also thicken the uterus lining to receive the fertilized egg. This phase is controlled by Estradiol hormone.

The ovulation phase:

It occurs in the middle of your menstrual cycle where a mature ovarian follicle opens up to release an egg for fertilization. It is the most sensitive phase where a woman has a great chance to become pregnant.

The Post Ovulatory Or Luteal Phase:

It is the last phase, which begins after ovulation and ends either in pregnancy or in the next menstrual cycle. In this phase, the uterus lining turns thicker prepare for pregnancy.

The luteal phase lasts from 10 to 16 days with the average being 14 days. But if it is less than 12 days, it is hard to become pregnant. The length of the phase varies from woman to woman but usually remain consistent from cycle to cycle.

The infertility period depends on the lifespans of both egg and sperm. In an average 28-day menstrual cycle, ovulation occurs on the 14th day. For women whose cycle is between 26 and 32 days, it could occur anytime between 12th and 19th day.

A sperm can remain alive for 3 to 5 days in the reproductive tract. Therefore, there is a high possibility to conceive if you have unsafe sex five days before ovulation time. The egg remains alive for only 24 hours, and if the fertilization does not occur within that time, it will die away.

Different methods to calculate safe period to have sex

You need to be careful while calculating safe period because doing it on your fingers or in the air could lead to wrong results. Remember that you must avoid sex or use condoms, cap, diaphragm or other contraceptive methods during unsafe days.

Use these proven online calculating methods to know your safe days:

Safe Period Calculator

Fertility awareness-based methods

Safe Period Calculator:

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 helps you find the safe and unsafe dates for having sex.

Click here for the OvulationCalc

Who can use safe period calculator?

You can use this method if the average length of your menstrual cycle from the past six months is between 26 and 32 days, and the variation between the shortest and longest cycles is seven days or less. The expected failure rate of this method can be as high as 10% per user per annum.

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 days or more.

After childbirth, you can use this calculator only after six regular menstrual cycles.

Teens and women reaching menopause cannot rely on this method.

Fertility Awareness-Based Methods (FAM):

Fertility awareness, also known as natural family planning, is a way of predicting safe and unsafe days of your menstrual cycle. These methods are usually based on certain signs your body gives in response to the hormones that cause ovulation.

FAM are based on the below assumptions:

One egg is released in each cycle.

Egg lives up to 24 hours.

Sperm lives up to six days and can fertilize an egg during this period.

A woman will be fertile for almost six days before ovulation and two to three days after ovulation, so the total number of fertile days is seven to eight in each cycle.

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.

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.

Ovulation Predictors: You can also get test kits that help predict ovulation. They are very helpful in planning pregnancies. However, you cannot completely depend on them to avoid pregnancies.

Emergency Contraception: If you have unprotected intercourse on a fertile day, then use an emergency contraception. It helps prevent pregnancy if taken up to five days after unprotected sex. The earlier you take it, the better it works.

What Are The Different Fertility Awareness-Based Methods?

There are several FAMs to keep you away from unwanted pregnancy. They also assist you to track your fertility patterns when trying to conceive.

Basal Body Temperature Method: It depends on your body temperature, which you need to track every day to know when you ovulate. There will be a rise in temperature during ovulation.

Cervical Mucus Or Ovulation Method: It involves checking the changes in the cervical mucus every day in the first stage of menstrual cycle until you ovulate. The vaginal discharge changes when you ovulate.

Calendar Or Rhythm Method: Here, you will chart your menstrual cycles on a calendar to predict ovulation based on the past cycles.

Sympto-Thermal Method: This is the most efficient method since it is a combination of all the above. It involves basal body temperature, mucus, calendar methods along with tracking cervix changes, abdominal heaviness, breast tenderness, slight spotting and mild abdominal pain.

Standard Days Method: If your menstrual cycle falls in between 26 and 32 days for a long time, this method works to record your monthly periods and determine your fertile days. Here, your unsafe days will be 8 to 19.

Let us understand all these methods in detail:

Basal Body Temperature (BBT) Method:

You will have low temperature in the initial phase of your menstrual cycle. It increases slightly after you start ovulating. The body temperature remains high for the remaining part of the cycle. It falls again before you start your next period. Tracking your temperature day by day will help you understand when you can ovulate. You should not have unprotected sex for three days after ovulation so as to avoid pregnancy.

BBT is your body temperature when you are at rest. It differs from woman to woman but is usually between 96 and 98 degree Fahrenheit before ovulation and rises to 97 to 99 degree Fahrenheit after ovulation. Even if you find any deviations, they will be in fractions like 1/10 to ½ of a degree.

Use a unique large-scale thermometer, which can mark 96 to 100 degree Fahrenheit and is easier to read. You will get the basal thermometer in most drug stores for around $10. Rectal thermometers are more reliable than oral or any other types.

How to check the temperature:

Take your temperature:

Note your temperature every day in the morning before you get out of the bed. Make sure you do not talk, eat, drink, have intercourse or smoke before taking the temperature. Keep your thermometer for about five minutes and then note the reading.

Chart the temperature pattern:

Record the reading in a chart, which you can get from a women’s health center or your doctor. Over the days, you can observe a pattern in your temperature. The increase in the temperature may be gradual, sudden or intermittent. The pattern will differ from one cycle to another cycle.

The factors that may affect your pattern, i.e. your temperature are:

Being upset, having improper sleep, stress, illness, smoking, jet lag, drinking excessively or using an electric blanket. You should mark all these events on the chart to understand the pattern.
In the beginning, you may take the help of your doctor, family planning specialist or a nurse to read the graph. Make sure you chart at least three months before using this method to avoid pregnancy.

Safe/Unfertile Days Using BBT Method:

The safe days are when the temperature is normal. The unsafe days start on the day the temperature rises and last for at least three days. They end once the temperature falls before your next period starts.

The Effectiveness Of BBT Method:

It is good at predicting when you can ovulate, but it cannot give you the exact day.

As the temperature does not rise until you begin to ovulate, you need to ensure that the sperm is not waiting in your body to mate with the egg. As mentioned earlier, sperm can be active for about five days in your body.

Combine BBT with any other FAM to be safe.

2. Cervical Mucus Or Ovulation Method:

The hormones which control the menstrual cycle also stimulate the cervix to produce mucus. It usually gets collected in your cervix and vagina. It changes its amount and consistency just before and during ovulation. You can learn to recognize its changes so as to predict fertile and unfertile days. This method is also called the Billings method.

Here Is How You Do It:

Check Your Mucus Pattern:

While you menstruate, the flow covers the mucus.

After your menstruation, there will be no mucus production for a few days which are usually referred as ‘dry days.’ These are considered to be safe days if your cycle is longer.

When the egg begins to ripen, you will produce more mucus, which you can see at the vaginal opening. It will be white, yellow or cloudy and you can feel it to be sticky.

You will have more mucus just before you ovulate, and it looks clear and slippery. If you hold it between your fingers, it stretches. This property is known as Spinnbarkeit, a German word for fibrosity and stretchiness. This indicates your peak fertility days.

You will have about four days with slippery mucus, and then there will be a sudden fall in the flow. You will have a few dry days before your next period.

Chart The Mucus Pattern:

You can mark your mucus patterns on a calendar every day. Mark your period days, dry days, sticky days, wet days and slippery days. You can notice that your mucus will be different at every stage. You can understand it better if you have someone to help you learn the pattern.