When is a woman the most fertile?

Each month women are prettier one or two days than usual, and this has been proven to coincide with the peak of their fertility.

Fortunately, other methods are also available if someone wants to know if they are in the fertile phase of their cycle. Now we take these methods in a row including fertile saliva ferning patterns but let’s clarify a few things first.

6 fertile days per cycle

The probability of becoming pregnant is highest in the five days before ovulation and on the day of ovulation. In 1995, 221 women who wanted a child were asked to record the days they had intercourse without contraception.

The exact day of ovulation was determined from urine samples based on the hormones estrogen and progesterone. A total of 629 cycles were studied, during which 129 babies were born out of 192 pregnancies.

The pregnancies with only one occasion of sexual intercourse were examined separately. These all occurred five days before ovulation or on the day of ovulation.

Based on all cycles, that includes when couples have sex multiple times, they also estimated the chances of conceiving on a given day.

Estimated probability of conception on the days of the menstrual cycle relative to the day of ovulation

The study concluded that sperm survive in the female body for up to five days after intercourse. After ovulation, the ovum can be fertilized for up to 1 day. Thus, these six days are the fertile phase of the cycle.

The most fertile day

The fertility peak is two days before ovulation.

We know this from a 2007 study in which 728 pairs were examined based on baseline body temperature. They were similarly asked to record the days of unprotected intercourse. The body temperature test does not show precisely which day the ovulation was, because it must be estimated retrospectively. However, the six-day fertility window can also be seen here.

Estimated probability of conception on the days of the menstrual cycle relative to the day of ovulation

Examining the 5390 cycles and 434 pregnancies, the study came to the conclusion that if we know the day of ovulation, it is worth scheduling the being together two days in advance. This is the best chance of conception.

Ovulation prediction

If we understand what hormonal processes are going on in our body and pay attention to the signs that accompany them, we can estimate the day of ovulation.

As a first step, estrogen levels in the body begin to rise, and in parallel, the salinity of body fluids increases. Then you should pay attention to the following:

  1. cervical softness, position,
  2. consistency of the cervix,
  3. increase in mucus and saliva electrolyte levels,
  4. crystallization of salts in mucus and saliva samples.

These methods including the fertile saliva fern pattern can indicate 3-4 days earlier that our body has begun to prepare for ovulation. In addition, there are less measurable signs such as a more attractive appearance, higher sexual desire, and e.g. greater sensitivity to odors.

As a second step, the pituitary gland releases large amounts of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) into the bloodstream. As a result, ovulation may occur 1 to 1.5 days later. At the same time, baseline body temperature, heart rate, and respiration increase, and LH can be detected in the urine. So these signals predict ovulation approx. 1 day in advance.

As a third step, the enlarged dominant follicle shrinks in size and develops a corpus luteum. Estrogen production is also reduced and progesterone production is started, which aids in implantation. The size change of the follicle is clearly visible by ultrasound examination. Therefore, clinics examine the dominant follicle with ultrasound on a daily basis, it is clear from this whether ovulation has occurred or missed.

Is there a cycle without ovulation?

Sometimes the first two steps take place, but ovulation does not occur. The frequency of ovulation decreases with age.

However, keep in mind that two ovulations are possible in one cycle. This occurs in 1-2% of cases. However, both eggs are not always fertilized. Just think of how rarely do we meet fratenal twins.

To conceive, on the other hand, you need to ovulate, that is, you need a mature egg ready to be fertilized. Since the cell released from the ovary lives for about 1 day, while the sperm can wait for 3-5 days, good timing is needed for success.

Home ovulation tests

With regular cycles, body temperature or urine tests can work great. These products measure changes in basal body temperature and / or urinary LH by approx. 1 day before ovulation. The data is collected by a mobile application that comes with the product for 3 months. It then calculates and signals when the fertile phase begins. This, in turn, means that the most fertile day is not indicated by actual hormone changes, but by data measured in the past.

With irregular cycles, we can only rely on an increase in estrogen levels a few days before ovulation. Unfortunately, approx. 1/3 of women has irregular cycles that depend on age, health, lifestyle and weight.

Nonetheless, more and more people are using methods to measure the rise in estrogen levels. Of these, there is already a mobile application for the ovulation saliva test and for the changes in electrolyte levels.

ovulation microscope

Using an ovulation microscope, fern-like patterns, crystals in saliva can be observed. Many women can determine fertile days based on this. Of the applications, however, only Babyndex is able to recognize fertile saliva fern patterns. At the current stage of development, it shows the probability of the occurrence of crystals, but it will soon indicate the peak of fertility in a personalized way. According to a study by Harvard Medical School, the ovulation saliva test can predict ovulation with 99% accuracy by image recognition of crystals. The Babyndex application aims to help more and more women in identifying the most fertile saliva fern pattern.

Measuring electrolyte levels requires an order more expensive devices. The first mobile applications for these enter the markets now.

So when can I get pregnant?

When the body begins to prepare for ovulation, it is possible to get pregnant. The peak of fertility is two days before ovulation, but the exact day cannot be known in advance. In fact, it may be omitted.

Changes in body fluids predict ovulation first e.g. during the fertile phase saliva ferning patterns predict it. The Babyndex application recognizes these patterns as not only women are prettier at the peak of fertility, but also their crystals.


How to use Babyndex for Ovulation Prediction

Babyndex makes Saliva Ovulation Test easy to use and increases its accuracy

You need an ovulation microscope 

Babyndex is the first digital saliva test. The mobile application can automatically interpret the saliva test, for which we supply an ovulation microscope

Take off the removable lens, add a drop of saliva to the glass and allow the saliva to dry. In about 10 minutes, put the lens back, press the built-in LED light button. You can read your body’s signals just by viewing the sample through the microscope.

full ferning

Depending on where you are in your monthly cycle, you can see dots and circles, fern-shaped crystals (full or partial) or a combination of these. These patterns get denser and sharper towards ovulation; in other words the probability of crystals increases.

Babyndex can automatically detect saliva patterns

Instead of viewing the patterns yourself, use the Babyndex app to detect the fern-shaped crystals in your dried sample.

Just take a photo with the app and it calculates the probability of the fern-shaped crystals. It also stores your photos and shows the results for each day when you took the test. The app can help you find out whether or not you may be near your actual ovulation.  

The saliva test shows the fertile window

The increasing probability of fern-shaped patterns in your dried sample predicts ovulation. 

The fertile window is the day of ovulation and the five days beforehand. These are your most fertile days of your menstrual cycle. Having intercourse during this time gives you the best chance of getting pregnant.

The saliva test is not perfect, though, and you might fern outside of this time period or when you are pregnant. However, if you are ovulating or about to ovulate, the crystal-like patterns appear on consecutive days. Seeing day-after-day high crystal probability helps you identify the fertile window in your cycle.

Use Babyndex every day for a full cycle 

At the beginning, you need to do the saliva test every day for a full cycle. This is the only way to find out if the test works well for you. 

Later, start doing the test daily before you expect to be in the most fertile days of your menstrual cycle. You will get your best results when you use the test within the five-day period around your expected ovulation.


  1. Test in the morning when your hormone levels are high and never test after eating, drinking, smoking, or brushing teeth.
  2. Clean the lens before using the test and carefully remove it by pulling it out of the casing.
  3. Place a drop of saliva on the surface of the lens.
  4. Allow the saliva sample to dry for about 10 minutes and then replace the lens into the housing. 
  5. Hold to the lens against the camera of your mobile and push the light button to take a picture with the Babyndex app to see the results.
  6. Clean the lens after every use (with a clean soft cloth or lens cleaner).

Common mistakes 

Babyndex will soon detect bad samples and help you adjust the amount of saliva that you need to add to the glass of the lens and the time to wait for the sample to dry. Until then please refer to the following common mistakes and try to avoid them.

Too little sample

When you collect too little saliva, there are some visible sharp details. But the amount of saliva is not enough for crystals and other artifacts to be seen.


Too much sample

When you collect too much saliva sample, there are many visible sharp details. But the amount of saliva makes it impossible to distinguish structural patterns, crystals and other artifact from each other. Avoid creating air bubbles.


Too wet sample

When you collect the right amount of saliva sample but you do not wait for it to dry, there are visible details but they are blurred and not sharp. This mistake is quite common; please remember that the saliva sample has to be dry for structural patterns to develop and to be seen. Allow the saliva sample to dry for about 10 minutes after that you can replace the lens into the housing. 



Advantages of Babyndex 

The analogue saliva ovulation predictor tests are hard to interpret and cannot reach their real potential in real use. 

Babyndex is the first digital saliva test that can detect changes of patterns in dried saliva samples. It can automatically interpret the saliva test results and can help you plan to become pregnant

Harvard researchers concluded in a 2018 study that the accuracy of the same solution as Babyndex is higher than 99 %. Using our method, we detect estrogen hormone increases in a much less intrusive and more affordable way than comparable urine or electrolyte tests. 

Babyndex should not be used as a contraceptive device

Near your time of ovulation, your dried saliva may form a fern-shaped pattern due to the increase of your estrogen and salt levels. The visible fern-like crystals begin to appear around 3 to 4 days prior to ovulation and you need a small microscope to see them. The saliva test allows you to predict ovulation by viewing these structural changes in your dried saliva. 

In 2012, the FDA approved the saliva test for ovulation prediction.

While other sites advertise saliva tests as a means of contraception, we do not advise you to use the saliva test to help prevent pregnancy, because it is not reliable for that purpose. 

In addition, if your test is positive and you know your most fertile days, it does not mean you will definitely become pregnant.


Interpreting Saliva Fern Test for You!

Getting pregnant sounds the most natural and almost automatic thing, but this could not be farther from the truth. According to a 2013 study, one in six couples has a hard time conceiving despite a year of trying. For them, this seemingly natural process turns into a dedicated and planned activity, which starts with monitoring their fertility window. While there are several ways, how we can learn about the ovulation cycles that are different from individual to individual, the saliva fern test is quite likely the most natural and non-intrusive method.

Saliva crystals tell you your fertile window

Every female body is experiencing a cyclical transformation every month. Depending where you are in your ovulation cycle, things change in your body. One of those is the level of estrogen, which increases near your time of ovulation. If we are able to spot this increase in estrogen, we can find out when we are entering our most fertile window – and we can find the answer in a single drop of dried saliva.

When our saliva dries, it causes crystals, but when we have increased estrogen – which happens 4-5 days before the ovulation – the crystals form a fern-shaped form. We can observe this with a dedicated handy ovulation microscope. If we put a saliva on the glass, allow it to dry and then look through the microscope, we can observe different patterns that saliva crystals make. What you would normally see are dots and circles, a full or partial fern or a combination of all the previously mentioned things. This all depends on where you are in your monthly cycle.

However, this might be somewhat difficult to interpret on your own – fernization occurs in different forms and different intensities and because of that the traditional saliva fern test boasts only 70-80% accuracy. The problem is not that much in the method itself, rather than in the interpretation that is difficult. The formation of fern-shaped crystals itself offer above 99% accuracy, so if we are able to improve the interpretation of the results, we could instantly improve the precision and reliability of saliva fern test.

This is precisely what Babyndex is doing by employing simple-to-use technology (ovulation microscope and an app on your smartphone) with an advanced algorithm that analyses and interprets your saliva crystals. This precise information can be used to help you become pregnant and to find out reliably when you are in your most fertile part of your menstrual cycle.

Interpret and predict ovulation with Babyndex

Babyndex application on iPhone or Android smartphone enables us to interpret the crystal patterns and based on this provide prediction as to when you are going to enter your fertile part of the ovulation cycle. Instead of you having to look through the microscope, simply place the microscope on your phone camera, take a picture and let the application do the rest.

The whole process – putting saliva on the glass, allowing it to dry, taking a picture and waiting for the results – only takes a couple of minutes and it can be done with same equipment day after day. The more information and images of your saliva it has, the more precise the algorithm will in in prediction your next fertile window.

Because of this repeat-ability and because it uses only a simple small microscope and a smartphone that you already have, it also provides an affordable way to learn more about your body and help you plan your parenthood in a more precise and – hopefully – successful way.

Of course, with Babyndex you can learn when you are going to be in your most fertile part of ovulation cycle and it does not guarantee that you will definitely become pregnant.