How To Calculate Periods Safety To Avoid Pregnancy?

Methods of determining infertile days or Safe days to avoid or delay pregnancy is in use for thousands years as a natural birth control method. Studies shows that implementation of modern scientific knowledge along with these calendar based charts will improve the accuracy of safe period calculation methods. The idea behind safe period calculator is to prevent or delay unwanted pregnancy naturally without any side effects. Currently there are several methods of natural family planning, like rhythm method and mucus method are used by peoples around the world and they are less reliable as a birth control method.

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

Calculating Safe Period Days :

The menstrual cycle, is commonly divided into three phases: the follicular phase (pre-ovulatory phase), ovulation, and the luteal phase (post-ovulatory phase). The length of each phase varies from woman to woman and cycle to cycle, though the average menstrual cycle is 28 days. Menstrual cycles are counted from the first day of menstrual bleeding.

In this safe period calculator, days 1 to 7 and day 21 to rest of the cycle is calculated as “Safe Period” or “safe days” for individuals with regular 26-32 days cycles. Please read the method overview for more information. Proper use of Safe Period Calculation method along with coitus interruptus (withdrawal method or pull-out method) is a suggested as a sin free or green family planning method for couples with self control over sexuality. Withdrawal method is not suggested for adolescents or those having casual sex. Others may use condoms during unsafe days to avoid serious and potentially life-threatening risks associated with the use of contraceptive pills.

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

What Are The Stages Of Menstrual Cycle:

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

1. The Pre-Ovulatory (Follicular Phase):

The follicular phase (or proliferative phase) is the phase of the menstrual cycle; before ovulation, during which follicles in the ovary mature. It ends with ovulation. The main hormone controlling this stage is estradiol.

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 .

2. The Ovulation Phase:

Ovulation is the process in a female’s menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum. The time immediately surrounding ovulation is referred to as the ovulatory phase. A woman gets pregnant around the days when ovulation occurs.

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.

3. The Post-Ovulatory (Luteal Phase):

The luteal phase (or secretory phase) is the latter phase of the menstrual cycle. It begins with the formation of the corpus luteum and ends in either pregnancy or degradation of the corpus luteum. The corpus luteum is a temporary endocrine structure, involved in production of estrogen and progestogen, which is needed to maintain the endometrium, the inner membrane of the uterus.

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.

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:

  1. Safe Period Calculator
  2. Fertility Awareness-Based Methods

1. 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.

Who Can Use Safe Period Calculator?

Check with your doctor about the effectiveness of natural family planning methods before using safe period calculator as a natural birth control method. Expected perfect use failure rate for this method is 3 – 4% per year.

If your average menstrual cycle length in last 6 months falls between 26 and 32 and the variation between the shortest cycle and longest cycle during this time is 7 days or less, you may utilize the safe period calculator method for birth control.

Who Can’t Use Safe Period Calculator?

If your average menstrual period length is less than 26 days or more than 32 days and the variation between the shortest cycle and longest cycle during past six periods is 8 days or more, you may not use this method.

Soon after child birth: you must wait for 6 regular periods, before using this method.This method is not recommended for teens and those reaching menopause.

2. Fertility Awareness-Based Methods (FAM):

Fertility Awareness Methods are also referred to as FAM birth control or “natural family planning”. They consist of keeping track of ovulation (the release of an egg) and timing sexual activity so it coincides with times of the month which are less conducive to pregnancy. In this way, a woman can abstain from sex or use extra protection during times in which she is most fertile.

There are several different types of methods women use to keep track of their fertility.

These include the Temperature Method, Cervical Mucus Method, Calendar Method, Standard Days Method and Sympto Thermal Method.

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.

What are the different kinds of FAMs?

Fertility awareness methods help you track your menstrual cycle so you’ll know when your ovaries release an egg every month (this is called ovulation).

The days near ovulation are your fertile days — when you’re most likely to get pregnant. So people use FAMs to prevent pregnancy by avoiding sex or using another birth control method (like condoms) on those “unsafe,” fertile days.

There are a few different FAMs that help you track your fertility signs. You can use 1 or more of these methods to predict when you’ll ovulate:

  • The Temperature Method: you take your temperature in the morning every day before you get out of bed.
  • The Cervical Mucus Method: you check your cervical mucus (vaginal discharge) every day.
  • The Calendar Method: you chart your menstrual cycle on a calendar.

It’s most effective to combine all 3 of these methods. When used together, they’re called the symptothermal method.

The Standard Days Method is a variation on the calendar method. You track your menstrual cycle for several months to figure out if your cycle is always between 26 and 32 days long — you can’t use this method if it’s longer or shorter. Once you’ve established that your cycle is in the right range, you use another form of birth control (or don’t have vaginal sex) on days 8-19, which is when you’re fertile.

Let us understand all these methods in detail:

1. Basal Body Temperature (BBT) Method:

The basal body temperature method — a fertility awareness-based method — is a type of natural family planning. Your basal body temperature is your temperature when you’re fully at rest. Ovulation may cause a slight increase in basal body temperature.

You’ll be most fertile during the two to three days before your temperature rises. By tracking your basal body temperature each day, you may be able to predict when you’ll ovulate. In turn, this may help you determine when you’re most likely to conceive.

If you’re hoping to get pregnant, you can use the basal body temperature method to determine the best days to have sex. Similarly, if you’re hoping to avoid pregnancy, you can use the basal body temperature method to help determine which days to avoid unprotected sex. Because the basal body temperature method alone doesn’t provide enough warning time to effectively prevent pregnancy, it’s generally used in combination with other fertility awareness-based methods if you’re hoping to avoid pregnancy.

How To Check The Temperature:

Tracking your basal body temperature doesn’t require special preparation. However, if you want to use the basal body temperature method for birth control, consult your health care provider first if:

  • You recently gave birth or stopped taking birth control pills or other hormonal contraceptives
  • You’re breastfeeding
  • You’re approaching menopause

To use the basal body temperature method:

  • Take your basal body temperature every morning before getting out of bed.Use a digital oral thermometer or one specifically designed to measure basal body temperature. Make sure you get at least three hours of uninterrupted sleep each night to ensure an accurate reading.

You may consider taking your temperature vaginally or rectally if you have trouble determining a pattern or change in your basal body temperature. For the most accurate results, always take your temperature using the same method.

  • Plot your temperature readings on graph paper. Record your daily basal body temperature and look for a pattern to emerge. Your basal body temperature may increase slightly — typically less than a 1/2 degree F (0.3 C) — when you ovulate. You can assume ovulation has occurred when the slightly higher temperature remains steady for three days or more.
  • Plan sex carefully during fertile days. You’re most fertile about two days before your basal body temperature rises, but sperm can live up to five days in your reproductive tract. If you’re hoping to get pregnant, this is the time to have sex. If you’re hoping to avoid pregnancy, unprotected sex is off-limits from the start of your menstrual period until three to four days after your basal body temperature rises — every month.

Benefits of basal body temperature:

As with other fertility based awareness methods, the benefits of basal body temperature monitoring include:

  • It is a natural method and does not cause side effects;
  • Women become more knowledgeable about their body changes which occur during their menstrual cycle when they use the method;
  • Correctly used, it provides highly effective contraceptive protection.

Limitations of basal body temperature:

The limitations of basal body temperature include:

  • It is unsuitable for use while the woman has a health condition which causes her temperature to rise, for example an infectious illness;
  • It requires daily monitoring of body temperature and measurements to be taken at the same time each day;
  • The fertile period begins at the beginning of the menstrual cycle (as opposed to other fertility based methods in which the woman can determine if she is infertile for the first 5-7 days of the cycle). The period in which abstinence or other contraception are required is therefore longer;
  • The method does not protect against sexually transmitted infections (STIs). Women who have sexual partners of unknown STI status should be advised to use male or female condoms to reduce their risk of contracting an STI.

2. Cervical Mucus Or Ovulation Method:

The cervical mucus monitoring methods of contraception are methods for preventing pregnancy which rely on a woman monitoring changes in her cervical mucus throughout the menstrual cycle. As the presence and nature of cervical mucus varies at different stages of the menstrual cycle, in response to changing hormone and fertility levels, women can determine when they are and are not fertile, based on the changes in their cervical mucus.

In order for the method to work effectively as a contraceptive, women must then abstain from vaginal intercourse during the fertile period of the cycle or use alternative methods of contraception if they have sex.

Who can use the cervical mucus method?

Cervical mucus monitoring methods of contraception are suitable for all women who experience menstrual cycles and are able to monitor changes in their cervical mucus on a daily basis (e.g. they are comfortable to touch their bodies and insert their fingers into their vagina). Use of these methods should be delayed however for women who have:

  • Recently used emergency contraceptive pills – These women should delay use until normal vaginal secretions return, usually at the start of the next menstrual cycle;
  • Who have recently given birth – These women should delay until regular menstrual cycles return, typically six months for breastfeeding and four weeks for non-breastfeeding women; or
  • Who have an unusual vaginal discharge – These women should have the discharge checked by a health professional, as it may indicate a serious condition such as a sexually transmitted infections. They should delay use of cervical mucus monitoring methods until the discharge has resolved.

Effectiveness of the cervical monitoring methods

When used correctly, the two days cervical monitoring method is 96% effective in preventing pregnancy in the first year of use, while the ovulation method is 97% effective. In addition, research indicates that women become more confident with the monitoring process over time, and this may increase effectiveness in the long term. The effectiveness of both methods decreases if they are not used correctly (e.g. if unprotected intercourse occurs in the fertile period).

Benefits of the cervical mucus:

The benefits of cervical monitoring methods include:

  • They are natural and do not cause side effects;
  • They do not require any special devices or procedures and do not cost anything;
  • Women become more knowledgeable about their menstrual cycle when they use the method;
  • The are suitable for women with irregular cycle lengths (cycle <26 days or >32 days) who cannot used calendar based methods;
  • The two days method is simple and requires minimal monitoring of cervical mucus changes.

Limitations of the cervical mucus:

The limitations of cervical mucus monitoring methods include:

  • Women must monitor changes in their cervical mucus on a daily basis in order to use the methods effectively. This makes the methods inappropriate for some women (e.g. those who have unusual vaginal discharge or are not comfortable checking for secretions or, for the ovulation method, those who are unable to check at certain times of the day) and difficult to use during some stages of the menstrual cycle (e.g. days of heavy menstrual bleeding);
  • The ovulation method requires women not only to monitor for the presence of cervical mucus but also to note changes in its consistency, and is therefore more difficult than the two days method to use;
  • The ovulation method may require changes to sexual practice (e.g. not having sex two days in a row in the first half of the menstrual cycle and only having sex in the evenings);
  • Additional contraceptive methods or abstinence are required if couples wish to have vaginal intercourse in the fertile period;
  • The methods do not protect against sexually transmitted infections (STIs), Women who have sexual partners of unknown STI status should, whenever possible, use male or female condoms to protect against STIs.

3. Calendar Or Rhythm Method:

The rhythm method, also called the calendar method or the calendar rhythm method, is a form of natural family planning.

To use the rhythm method, you track your menstrual history to predict when you’ll ovulate. This helps you determine when you’re most likely to conceive.

If you’re hoping to get pregnant, you can use the rhythm method to determine the best days to have sex. Similarly, if you’re hoping to avoid pregnancy, you can use the rhythm method to determine which days to avoid unprotected sex.

Using the rhythm method for birth control requires careful record keeping and persistence. If you don’t want to conceive, you and your partner must avoid having sex or use a barrier method of contraception during your fertile days each month.

Why it’s done?

The rhythm method can be used as a way to promote fertility or as a method of contraception, by helping you determine the best days to have or avoid unprotected sex. Some women choose to use the rhythm method if a complex medical history limits traditional birth control options, or for religious reasons.

Risks Of Calendar Or Rhythm Method:

The rhythm method is an inexpensive and safe way to help you chart your fertility — the time of month when you’re most likely to be able to get pregnant.

Using the rhythm method as a form of birth control doesn’t pose any direct risks. However, it’s considered one of the least effective forms of birth control. How well the rhythm method works varies between couples. In general, as many as 24 out of 100 women who use natural family planning for birth control become pregnant the first year. Also, the rhythm method doesn’t protect you from sexually transmitted infections.

How to Use the Calendar Or Rhythm Method?

  • Record the length of 6 to 12 of your menstrual cycles. Using a calendar, write down the number of days in each menstrual cycle — counting from the first day of your period to the first day of your next period.
  • Determine the length of your shortest menstrual cycle. Subtract 18 from the total number of days in your shortest cycle. This number represents the first fertile day of your cycle. For example, if your shortest cycle is 26 days long, subtract 18 from 26 — which equals 8. In this example, the first day of your cycle is the first day of menstrual bleeding and the eighth day of your cycle is the first fertile day.
  • Determine the length of your longest menstrual cycle. Subtract 11 from the total number of days in your longest cycle. This number represents the last fertile day of your cycle. For example, if your longest cycle is 32 days long, subtract 11 from 32 — which equals 21. In this example, the first day of your cycle is the first day of menstrual bleeding and the 21st day of your cycle is the last fertile day.
  • Plan sex carefully during fertile days. If you’re hoping to avoid pregnancy, unprotected sex is off-limits during your fertile days — every month. On the other hand, if you’re hoping to get pregnant, have sex regularly during your fertile days.
  • Update your calculations every month. Continue recording the length of your menstrual cycles to make sure you’re properly determining your fertile days.

Keep in mind that many factors, including medications, stress and illness, can affect the exact timing of ovulation. Using the rhythm method to predict ovulation can be inaccurate, especially if your cycle is irregular.

4. Symptothermal Method:

The Symptothermal Method (STM) is an effective, co-operative, scientifically-based and inexpensive method of natural family planning. It is based on the awareness of the fertility of the couple.

There are three main methods of natural family planning in Canada:

  • the Symptothermal Method,
  • the Billings Ovulation Method and
  • the Creighton Model.

The Symptothermal Method is the most trustworthy of all natural family planning methods because it incorporates several signs of the woman’s fertility: cervical mucus, cervix changes, morning temperature, and calculation to determine the beginning and the end of the fertile period. Select the menu item “How it Works” on the left to find out the details of how this method works.

So how is the sympto-thermal method different?

Enter the sympto-thermal method. We are lucky enough to have people that have devoted their lives to the research of the female reproductive system and hormones. Because of that, we know all of this:

  • Sperm need cervical fluid to survive, swim, and be effectively “washed” and capable of fertilizing an egg. It can live in fertile cervical fluid for up to 5 days, but dies quickly in the natural acidic vaginal environment.
  • Cervical fluid builds up in response to estrogen, which is released by the developing sacs that hold the egg. This is happening in the days leading up to ovulation.
  • The egg can only live for 12-24 hours, and ovulation can only happen once in a cycle. If two eggs are released, the second comes within 24 hours of the first, after which ovulation is inhibited by high levels of progesterone.
  • Progesterone is released from the corpus luteum, which is what the sac that held the egg turns into after ovulation has taken place. This raises the body temperature, dries cervical fluid, and inhibits a second ovulation.

I know right now some of that may still seem foreign to you, but let me go over what happens during a typical menstrual cycle.

5. Standard Days Method:

The Standard Days Method (SDM) relies on a fixed “window” of fertility that makes it easy for women to know when they are likely to become pregnant. To avoid pregnancy, a woman with menstrual cycles between 26 and 32 days long should either use a backup method of contraception or refrain from unprotected intercourse on cycle days 8 through 19. A color-coded string of beads, called CycleBeads, are used to help women keep track of the days of their menstrual cycle and identify which days they are likely to get pregnant.

The Effectiveness Of Standard Days Method:

In an efficacy study, SDM was found to be more than 95% effective. That means that out of 100 women using the method for one year, fewer than five of them would get pregnant if they used SDM correctly.

However, the study also found that women who do not keep careful track of their cycle days or have unprotected intercourse on days 8 through 19 of their cycles are much more likely to get pregnant. When pregnancies occurring with correct use and with incorrect use of the method were added together, the total was approximately 12 pregnancies for every 100 women/year of method use.

The effectiveness of SDM is similar to that of some other user-dependent methods of family planning.

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.

How effective are fertility awareness methods?

FAMs are about 76-88% effective: that means 12-24 out of 100 couples who use FAMs will get pregnant each year, depending on which method(s) are used. If you use multiple FAMs together, they work even better.

The better you are about using FAMs the right way — tracking your fertility signs daily and avoiding sex or using birth control on “unsafe” days — the more effective they’ll be. But there’s a chance that you’ll still get pregnant, even if you always use them perfectly.

Fertility awareness methods don’t work as well as other types of birth control because they can be difficult to use. Want a more effective way to prevent pregnancy? Check out IUDs and implants, or take this quiz to find the birth control method that’s best for you.

How can I make FAMs more effective?

Like all birth control methods, FAMs are more effective when you use them as perfectly as possible. How well FAMs work also depends on both partners, so it’s important that each of you is supportive and learns how to use the methods.

FAMs are most effective when:

  • you work with a nurse, doctor, or counselor who knows FAMs well to learn how to use them correctly
  • you have the time and discipline to check your fertility signs and chart your cycle every day
  • you and your partner don’t mind avoiding vaginal sex or using another kind of birth control around your fertile days

The best way to use FAMs is to combine the temperature, cervical mucus, and calendar methods. Each of these methods relies on different signs to predict your fertile days, so using them together gives you the best picture of your fertility and makes FAMs more accurate. For example, keeping track of your cervical mucus pattern can be useful if your temperature chart gets messed up because you’re sick or stressed. And using more than 1 method may help you narrow down your fertile days, so you will more safe days each month.

You can keep track of your mucus, days, and temperatures on a fertility awareness method chart like this one.

Advantages Of Using FAMs For Avoiding Pregnancy:

  • Inexpensive, convenient and safe to use (as no hormones or devices are used).
  • Develop communication, responsibility, and cooperation among partners.
  • Helpful in establishing an optimum fertility phase to plan a pregnancy.
  • Helps you track and improve premenstrual syndrome (PMS) symptoms.
  • Acceptable for those couples with religious concerns about artificial contraceptive methods.
  • No medications involved.
  • You can get calendars, charts, and thermometers easily.

Disadvantages Of Using FAMs:

  • The failure rate is high as an accurate prediction of fertility is difficult.
  • There will be no protection against sexually transmitted infections.
  • You should keep a close track of your infertile days.
  • Taking any medicine can affect the signs of these methods.
  • You should abstain from sex or use a contraceptive for about 10 fertile days in each cycle.

You Cannot Depend On FAMs If:

  • Your periods are irregular.
  • Your partner is not cooperative.
  • You have any STIs or abnormal vaginal discharge.
  • You cannot keep a track of cycles.
  • You are breastfeeding, in teenage or nearing menopause stage as hormonal changes may affect the signs.
  • You had recently taken a contraceptive.

There is no particular phase when a woman cannot get pregnant as ovulation and menstrual cycles are unpredictable at times. However, you can use certain fertility awareness based methods to track your safe sex days so as not to conceive.

Hope you have got a clear understanding of the safe period to avoid pregnancy.


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