Every month, a woman’s reproductive system undergoes a series of hormone mediated changes, that make it possible for pregnancy to occur. In the first phase of the menstrual cycle (follicular phase), estrogen levels rise gradually, resulting in the thickening of the uterine lining (to prepare for a possible pregnancy) and the growth and development of the oocyte (egg). Around the 14th day,the fully developed egg is released (Ovulatory phase) and is either fertilized by a sperm, resulting in a pregnancy, or is discarded along with the lining of the uterus, resulting in a period (luteal phase).
Usually, the egg is viable for about 24 hours after release. Male sperm cells, however, survive in the female reproductive tract for up to 6 days. So, chances of pregnancy are high, starting from the day before ovulation, lasting up to 6 days after ovulation.
Fertility awareness methods use physiological indicators to track the time of ovulation and by extension, the 5-7 days of the month when a woman has the highest likelihood of pregnancy.
Women might choose to track their fertility for a number of reasons:
Human body temperature is in a state of constant flux. The body constantly undergoes subtle changes in temperature, reflecting its metabolic patterns. Any number of factors such as exercise, food intake, sleep/wakefulness, stress levels, external temperature and so on, have a measurable impact on body temperature.
Basal body temperature (BBT) refers to the lowest temperature of the body, during a state of complete rest (deep sleep). Usually, a temperature reading taken immediately after waking up, even before getting out of bed, is the closest to the basal body temperature (although it is still slightly higher than the BBT).
Because there is so much variability in body temperature, it is vital that the readings used to track your monthly cycles pertain as closely as possible to the BBT and that there is as little variation as possible between them.
Most women record temperatures between 36.11-36.38°C [97-97.5°F] before ovulation and 36.44 to 37°C [97.6-98.6°F] right after ovulation, for up to 72 hours, unless pregnancy occurs, in which case, the elevation lasts throughout the first trimester.
Studies show that using BBT charts to track fertility has about a 99% success rate in the first year that most women use it (if done properly). However, following the first year, the success rate drops to about 85%. It is assumed that this is because of reduced assiduousness and care after the initial period.
BBT charting continues to be a widely used method to track fertility, owing to its affordability, universality and relative simplicity. It is vital to remember however, that there is no such thing as a universally ideal BBT curve. Every woman’s cycle bears its own little idiosyncrasies, which only come to light when the charting is done consistently over a period of time. It is only within the framework of a woman’s unique curves that useful trends are observed.
You shouldn’t be surprised to see numerous tiny peaks and troughs in your chart. However do bear in mind that you are looking out for a “curve”. I.e you are looking to find a biphasic pattern that has an ascending and descending trend. This means that after ovulation, the average temperature readings tend to be higher than average readings taken before ovulation.
Three consecutive, above-average readings usually indicate that ovulation probably occurred before the first high reading.
Generally, as a thumb rule, before you panic about your curve being abnormal, it is advisable to check if your thermometer might be faulty. Additionally, digital thermometers may give slightly-off readings for upto a month before their batteries die.
No, not necessarily. Although basal body thermometers are especially marketed towards women who are looking to chart their monthly cycles, any thermometer that is accurate and easy to read to within 1/100th of a degree, (if you use celsius - or 1/10th of a degree, for fahrenheit) can be used.
However, basal body thermometers do come with specialised features that might make them appealing for charting. Nevertheless, you might just find that a few frippery features don’t really justify the prices at which these thermometers are sold.
The future of healthcare is definitely one that minimises human effort and in turn, error. There is no doubt that medicine is rapidly moving towards a big-data revolution. The consumer of tomorrow will have to do/worry about less and conversely, will have access to more.
A slice of the future is here - With ONiO, collecting and charting your BBT, readings could not be easier. Readings are collected and tabulated constantly, to reflect trends in your temperature.