Helping You Monitor Your Fertility

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"In order to get the most out of your symptothermal charts, you need to understand what information is contained on those charts and how it is conveyed."


Ovulation Calendar


Symptothermal charts can come in many different formats. Some charts include fields for many different symptoms. Others may only include spaces for temperature and cervical mucus data. A given software package will describe its standard conventions. This page aims to introduce some common notations to help introduce paper and electronic charting.

Charting Overview

Almost all charts are organized with different symptoms appearing in a separate row or rows from the top to the bottom of the chart. Each column represents a day with the earliest date in the far left column.

Temperature Charting

Each temperature reading is recorded on the chart as a dot. There should be one dot per day. Each individual dot is connected to create a graph of temperature data. This makes interpretation easier by helping to identify the temperature patterns.

Circled Temps Indicate Possible Outside Influence Other information pertaining to your temperature data can also be recorded. This often includes notes for explainable temperature abnormalities. For example, a temperature may be high or low for reasons not related to hormonal changes of interest for BBT charts. This may include illness, taking your temperature late, trouble sleeping, etc. When a temperature value is questionable, it is typical to circle the temperature point. This is shown in the example to the right. Circling the temperature point makes it clear that the temperature may be treated with skepticism when interpreting the chart.

Sometimes women will record other optional information about their temperature data for information purposes. This may include the time the temperature was taken each day, whether or not the temperature was taken orally or vaginally, or if a new or different thermometer is being used. Since consistency is key when taking temperatures, you should not change thermometers or your method of taking your temperature in the middle of a given cycle.

Cervical Mucus

One or more rows are normally dedicated to cervical mucus. The individual recorded values can be indicated using different notation. A convention common for both paper and electronic charts is to use letters. A letter P is used to indicate period or menstruation. D indicates low fertility symptoms (dry, no mucus visible). M indicates moderate fertility characteristics (moist/sticky (M-), white (M-) or cloudy (M+), holds shape (M-) or slightly stretchy (M+)). Finally S indicates fertile characteristics (slippery, wet, thin, transparent, and stretchy).

P = Period    D = Dry    M = Moist    S = Slippery

These symptoms can be completely enumerated or combined into a single field on the chart. Combining all symptoms into a single letter attempts to collectively summarize the overall symptoms. The example above shows both. The top row collectively summarizes the individually specified symptoms which are shown in the lower rows.

Ovulation Test Results

Most charts also include a row to track ovulation test results. This row is left blank if no test is taken on a given date. If a test is taken and is positive, a positive sign (+) is recorded for the day. If the test is negative, a negative sign (-) is instead recorded.

+ Positive    - Negative    blank = Not Tested   

Cervix State Information

A separate row is reserved for cervix observations. These can be collectively summarized or completely enumerated as was the case for cervical mucus. Again letters are used to indicate different recorded values. A letter L indicates low fertility (low position, firm, closed). M indicates moderate fertility (between low and high, getting softer, and starting to open). The letter H indicates highly fertile symptoms (high position, soft, and open).

L = Low    M = Moderate    H = High   

The image above shows individual characteristics enumerated in the lower rows. The top row collectively summarizes the data overall. The chart can optionally show this row alone if the only the summarizing value is recorded.

Saliva Ferning

Saliva ferning can also be recorded on symptothermal charts if tracked. Letters are again used to distinguish between the degree of ferning. The letter N indicates that there are no ferning patterns. T indicates transitional ferning patterns. The letter F indicates complete ferning patterns indicative of increased fertility.

N = None    T = Transitional    F = Ferning   

Recorded Sexual Intercourse

It is customary to circle the cycle day number if sexual intercourse occurred on that date. This makes it possible to see when intercourse was recorded directly on your symptothermal chart. By checking intercourse against fertility signs, it is possible to gauge the likelihood of conception during a given cycle. It is also possible to speculate on a conception date using this same information after pregnancy has been achieved.

Circled Cycle Days Indicate Recorded Intercourse
Circled cycle days indicate sexual intercourse

Fertility Interpretation on Charts

Symptothermal charts can also contain indicators of fertility and ovulation. These are usually added as the patterns in recorded symptoms take shape for a given cycle. Some customary designators for chart interpretation are explained below. Electronic charting tools often add these indicators of analysis automatically. Some can even be drawn on paper charts.

Sometimes cycle days will be color coded to indicate a coarse estimate of fertility. These tend to be overly liberal or conservative depending upon how they are generated. These should ideally take into consideration all recorded symptoms. A legend usually identifies the meaning of the colors. The region marked fertile is often referred to as the Fertile Window. This is the time where couples should avoid or plan intercourse depending upon whether they want to avoid or achieve pregnancy.

Coarse fertility color coding.  Intercourse days are circled.
Coarse fertility assessment with intercourse days are circled. Copyright Image.  Used with permission.
Copyrighted Image.  Used with permission.
Color code for coarse fertility assessment and chart shading

When all symptoms are collectively considered, electronic charting software can estimate the most likely ovulation date. This central estimate of ovulation is indicated by circling the calendar day. The circle denotes ovulation and is shown in an example further below. Some software tools will allow users to manually specify this estimate of ovulation. It can even override the default calculation. When overriding the calculation, the circle may appear in a different color.

This collective assessment is important since individual symptoms may estimate ovulation differently. The following discussion will highlight how the ovulation estimate for separate recorded symptoms are indicated on charts.

Chart Shading as a Powerful Indicator of Fertility

One of the best interpretive features for couples new to fertility awareness is chart shading. This electronic technique overlays interpreted fertility levels directly on the symptothermal chart. The patterns are individually associated A chart shaded to indicate fertility. to each symptom. Lighter colors indicate low fertility and chances of getting pregnant. The darker shading indicates high fertility around the time of ovulation.

A shaded chart can quickly be understood. Dark regions indicate a high likelihood of conception. The shading pattern changes based upon the interpreted odds of getting pregnant. This is more informative than infertile or fertile labels since it accounts for more than just a black and white assessment of fertile versus infertile.

Since each symptom is shaded separately, couples can begin to see how individual symptoms relate to interpreted fertility. For example, the ovulation test result row in a chart is shaded to indicate when the likelihood of conception is greatest based upon positive test results. This is done separately from other recorded symptoms such as temperatures or mucus. This helps couples see how a given symptom contributes to their overall fertility assessment.

A shaded chart shades the background of each symptom to indicate the fertility assessment based upon that symptom. In addition to the symptoms with dedicated rows (temperature, mucus, cervix, ferning, etc.), the ovulation estimate from the calendar or rhythm method can also be depicted. This is commonly done by shading the row of calendar dates. The day with the darkest shading corresponds to ovulation based upon the rhythm method. This technique has its limitations, but can still be included to visually show when it agrees with other symptoms.

Interpretation of Recorded Temperatures

A cross hair mark is common put on the temperature grid of a symptothermal chart to identify ovulation based upon temperature readings. This is also described as a coverline although it is usually shown even if the coverline analysis technique is not used.

The vertical line separates the two phases of the menstrual cycle BBT Chart Interpretation by identifying where the temperature shifts. This coincides with ovulation. A horizontal line is usually included to help illustrate how the temperatures early in the cycle are generally lower than those in the second half. This line can also be extended when interpretation uses one of the coverline techniques.

Ovulation is coincident with the temperature shift. The cross hairs identify the location of this shift and therefore mark ovulation. Ovulation is usually assumed to be the day before the shift occurs (the date immediately to the left of the vertical line).

In the example above, notice how chart shading also helps to identify the increased odds of achieving pregnancy associated with ovulation based upon the temperature data.

Interpretation of Cervical Mucus

Cervical mucus is plotted and can also be shaded as an indicator of fertility. Each recorded value has fertility intrinsically associated with it. When considered as a whole, fertility levels can be calculated for each day based upon all cervical mucus readings throughout the cycle. These are customarily shown using chart shading if available.

The ovulation date can be estimated based upon cervical mucus observations. It is calculated to be the last day that exhibits fertile mucus (marked with an S for slippery or sometimes an F as shown below for fertile). An X is customarily placed over this date to mark it as the ovulation date based upon recorded cervical mucus symptoms.

An X is placed through the last F day
to mark ovulation based on CM records

Interpretation of Other Symptoms

Other symptoms such as saliva ferning and cervix observations do not include indicators on the chart. The individual recorded characteristics have fertility associated with them. Fortunately chart shading still makes it possible to visually show this relationship and consider the recorded symptoms collectively across the entire cycle. Shading can be used to highlight intervals of possible high fertility based upon these optionally recorded symptoms.

Other custom symptoms may also be recorded. These may include breast tenderness, ovulation pain, spotting, etc. In some women these other symptoms may also be indicative of ovulation. This is why it is helpful to include them on the chart. Since the relationship between them and ovulation is not universal, they are generally not interpreted or shaded. It is left up to the couple to look for patterns or consider implications based upon these other specific factors.

Fertile Window

The fertile window is typically indicated on a chart by drawing vertical lines. Days between the lines are considered to be fertile. Pregnancy is very possible within these dates. Outside of the fertile window, fertility is very low and pregnancy is rather unlikely (but not always impossible).

Sometimes electronic charting software will color the vertical lines that indicate the start and end of the fertile window. Light (gray) colored lines indicate an approximation of the start or end of the fertile window. Once this approximation is confirmed by additional information or symptoms, it is darkened (black). Keep in mind that the light colored lines may change as new daily symptoms are recorded.

Electronic Charting

An easy and convenient way to learn to chart your fertility is through electronic charting. You can enter your records into software that automatically generates charts for you. It can even help you interpret your charts. This approach is generally recommended for couples new to fertility charting. Even if you have charted in the past on paper, you may enjoy the ease of electronic charting.

More information about electronic charting is available on this site.

Example of an Electronic Symptothermal Chart
Image is Copyrighted. Used with permission by the Hormonal Forecaster.

Paper Charting

Paper charts come in many forms. If you do not already have a paper chart, you can get one from this site. If you have access to a computer, you can also consider charting electronically.