Introduction
Basal Body Temperature (BBT) tracking is a crucial component of Natural Family Planning (NFP), offering insights into a woman's fertility cycle. However, various factors can influence BBT readings, making it essential to understand what can affect this method's accuracy. If you can identify the factors affecting your BBT, then you can make adjustments to your lifestyle and temperature tracking to more accurately record your BBT spike. Therefore, you will be able to pinpoint when ovulation has happened so that you can be even more successful with NFP. After reading this blog article, make sure to make notes on your own personal BBT chart of any factors discussed that you may have experienced.
Understanding Basal Body Temperature
Definition: BBT is your body's temperature at rest. It is used in NFP to detect ovulation, as there is a slight increase in temperature after ovulation due to the hormone progesterone. After ovulation occurs, the BBT should rise by approximately 0.4-1.0 degrees Fahrenheit, and your temperature should remain elevated until the start of your next period.
Importance in NFP: Accurate BBT tracking can help identify ovulation in a woman's cycle. Understanding factors that can cause inaccurate temperature readings will help you to better interpret your BBT chart and make adjustments to better pinpoint when ovulation has actually occurred.
Factors That Can Affect BBT Readings
Inconsistent Measurement Times
BBT should be taken at the same time each morning after at least 3-5 hours of uninterrupted sleep. Three hours of uninterrupted sleep is the hard minimum, but ideally a woman should get at least 5 hours of uninterrupted sleep for the most accurate BBT readings.
Variations in timing can lead to inaccurate readings. This could be due to factors such as insomnia, having young children who frequently wake you up throughout the night, or having to get up throughout the night to breastfeed a newborn.
Illness or Fever
Any illness causing a fever can elevate your BBT, masking the ovulation-related rise. Therefore, if you know that you are currently sick and running a fever, make a note of this in your chart, and you may want to check your temperature a couple days after to confirm whether ovulation truly occurred, or if this was just a fever lasting a day or two.
Lifestyle Factors
Alcohol: Alcohol consumption the night before measuring BBT can cause an elevation. The specific amount of alcohol that could lead to an elevated BBT varies from person to person. Some women may only experience BBT elevation if they feel hung over the next morning while others may experience a rise in BBT from just a couple glasses of wine the night before. You will need to be diligent in recording amount of alcohol vs BBT while you are getting used to using this method of natural family planning to learn how it affects you. Once you determine the amount of alcohol that may cause BBT shifts for you, you should avoid drinking that amount of alcohol while you are anticipating ovulation during the follicular phase and fertile window. However, if you do drink to an amount that would affect your BBT during the follicular phase, you can make a note of it in your chart and see if your BBT remains elevated for the rest of the cycle (indicating that ovulation did, in fact, occur), or if it drops back down to normal the next day, which would indicate that the temperature shift was simply due to alcohol consumption. Once you have already confirmed ovulation in your cycle, temperature shifts within the luteal phase are not as important since you have already confirmed ovulation.
Night shift or a frequently changing work schedule: Shift work can prevent accurate BBT readings, especially if you are working night shift or consistently switching between day and night shift. If switching to consistent daytime hours is not possible for your job, then you may consider switching to a different method of NFP such as the cervical mucus method.
Interrupted sleep or oversleeping: Try to make sure that during the follicular phase, more specifically the fertile window, you get at least 3-5 hours of uninterrupted sleep and wake up at a consistent time so you can check your basal body temperature at the same time every morning while trying to detect your BBT shift. This may mean that while you are anticipating ovulation in your fertile window, your spouse can get up to feed the baby or tend to any little ones who may wake up in the middle of the night. This can help to ensure that during the time that you are getting close to ovulation, you are getting a minimum of 3-5 hours of uninterrupted sleep in order to better record an elevation in BBT. After ovulation has been confirmed, you can go back to your normal rotation of who gets up with the kids in the middle of the night.
Traveling and change in time zones: Traveling can cause stress in and of itself, which can lead to BBT fluctuations. Additionally, if you are changing time zones, you could be potentially waking up at different times than you are used to, and therefore not checking BBT at same time every day. Make sure to note any time zone changes that you have experienced on your BBT chart. During travel, you will want to be extra cautious when it comes to sex and identifying your fertile window and ovulation. You can either play it safe and try avoiding sex altogether during travel (if your goal is trying to avoid), otherwise, you can try to be extra observant of cervical mucus in order to use this as a back up method of identifying peak fertility and ovulation.
Medications
Certain medications, especially those that affect hormones, can influence BBT. Some medications that can cause BBT fluctuations include thyroid medications, stimulants (i.e. ADHD medication), fever-reducing medications, allergy medications, and some antibiotics.
Levothyroxine: Initiation of levothyroxine and dose changes of this medication are what can cause changes to your basal body temperature since it is affecting your thyroid hormone levels, which affect your metabolism and body temperature. However, after you have been on levothyroxine long enough that your TSH (thyroid stimulating hormone) level is normal and you have been titrated to a consistent levothyroxine dose, your basal body temperature should not fluctuate much.
Antihistamines (allergy medications): Allergy medications can affect BBT by making it more difficult to sweat. Decreased sweating can decrease your bodies ability to thermoregulate. Therefore, it has the possibility to cause increased BBT. With that being said, ever person is different, so while this type of medication may affect some individuals, other people might not notice any effect on body temperature.
Stimulants: Stimulants such as Adderall, which are used for treatment of ADD and ADHD, can raise your body's basal body temperature. Using these medications consistently for prolonged periods can cause your baseline temperature to be higher than normal. While your temperature may remain fairly stable if on these medications for an extended period of time, starting this type of medication may cause fluctuations in your BBT.
Fever-reducing medications: Medications such as Tylenol and NSAIDs (i.e. ibuprofen) are often used as pain relievers. However, these medications also have the effect to reduce fevers. Therefore, if you take these medications, they may falsely mask an elevation in BBT during ovulation. Try avoiding these medications as much as possible when you know that you are approaching ovulation in order to prevent missing your BBT spike.
Make sure to discuss any and all medications that you are taking with your NFP practitioner to find out if these could be affecting your BBT and therefore NFP charting. Additionally, keep an extra close eye on any changes in your recorded BBT when starting a new medication since different medications can cause temperature fluctuations.
Environmental Factors
Room temperature and sleeping conditions (such as using an electric blanket) can alter BBT.
Seasonal changes, particularly during extreme weather, can also affect your BBT readings.
Try to make sure your bedroom is a consistent temperature during all seasons to avoid any BBT fluctuations from happening.
Physical Activity
Engaging in vigorous physical activity or not getting enough rest before taking your BBT can result in higher readings.
Additionally, having sex immediately before checking your temperature can increase your BBT as well.
This is why it is important that you make sure to check your BBT first thing in the morning prior to any physical activity or sex. This will give you the most accurate BBT reading.
Menstrual Cycle Irregularities
Conditions like PCOS, endometriosis, or thyroid disorders that affect the menstrual cycle can also impact BBT patterns.
Make sure to discuss your past medical history with your NFP practitioner to get insight as to whether any known health conditions may be effecting your BBT readings.
If you know that you have any of these medical conditions and that they seem to be affecting your BBT, you may consider trying a different NFP method that does not rely on BBT. Otherwise, make sure that you are incorporating either cervical mucus observations or the sympto-hormonal method with basal body temperature. BBT alone can not determine the start of the fertile window, so it is generally advised to use a combination of these methods anyways in order to identify the beginning of your high fertility period.
Tips for Accurate BBT Tracking
Consistency: Take your temperature at the same time each morning, immediately after waking up and prior to doing any physical activity or having intercourse.
Use the Right Thermometer: A digital basal thermometer is recommended for its accuracy. Here is a digital BBT thermometer that I would recommend.
Chart Your Readings: Keep a daily log for pattern analysis. This can be done with different apps such as Natural Cycles, Tempdrop, or Premom. Otherwise, you can use paper charts as well. Some apps will automatically sync this information for you, but some other apps will require you to manually log your BBT reading.
Mind Your Health and Lifestyle: Note any factors that might have influenced your BBT directly on your chart. This can help you identify causes of any BBT irregularities, and it can also better help your physician to interpret your BBT chart.
When to Seek Help
If you consistently struggle with interpreting BBT charts or if you have concerns about menstrual irregularities or fertility, consult a healthcare professional.
Conclusion
Although this blog post may initially make BBT tracking feel daunting, my goal is to help you identify anything that could potentially throw off your readings in order to help make this form of NFP as effective as possible. By understanding these influences and maintaining consistent tracking habits, BBT can be a reliable indicator of fertility for many women. Being able to recognize your body's patterns and factors that influence your basal body temperature can help you adjust your lifestyle (especially during the follicular phase and fertile window) in order to have the most accurate and consistent BBT readings. Therefore, you will be able to properly pinpoint when ovulation has occurred.
Some BBT apps, which track your temperature throughout the night instead of requiring an individual to wake up at the same time each morning are Natural Cycles and Tempdrop.
For more information on when the follicular phase and fertile window occur, click here to read my blog post about the menstrual cycle (explains about the follicular phase) and click here to read my blog post about the fertile window.
References:
Comments