Early Ovulation Wilcox et al. (2000) estimated that 2% of women were in their fertile window by the fourth day of their cycle and 17% by the seventh day (based on 213 women). |
Late OvulationAn estimated 30% of OvuSense users have late ovulation - that is, an ovulation which occurs more than 65% of the way through a cycle. This estimate appears to be consistent with the findings of Wilcox et al. (2000) This pattern of a shortened follicular phase is more frequently identified in older women due to earlier dominant follicle selection - Klein et al. (2002) - study size 31 , and also correlates with a history of recurrent miscarriage - Jukic et al. (2007) - study size 201 |
Slow RiseA slow rise occurs in an estimated 5% of OvuSense users, and is characterised by a slow and steady increase in temperature over a number of days, rather than a steep rise over two to three days. A slow rise is generally related to Polycystic Ovarian Syndrome and/ or an indication of Polycystic Ovaries. However, it can also be a sign of Diminished Ovarian Reserve. A recurrent slow rise over 3 or more cycles without a previous diagnosis of either of these ovulatory issues would indicate the need for a formal diagnosis. |
Short Luteal PhaseA short luteal phase is deemed to be any ovulation that occurs 10 days or less before a subsequent onset of menstruation. This situation can occur with Polycystic Ovarian Syndrome but is not limited to that ovulatory issue alone. Short luteal phases are commonly seen at the extremes of reproductive life, at times of stress or due to other conditions such as thyroid disorders and stress. A short luteal phase in 2 or more cycles out of 3 would indicate a necessary treatment as women with a tendency to short luteal phase have a higher chance of miscarriage. |
Fertility tracker apps use the calendar based method of tracking. You input the dates of your period and the app will calculate your ovulation based on the assumption that you have 'middle of the month' ovulation. Some have more sophisticated algorithms which accept manually entered oral temperatures, or Luteinizing Hormone (OPK) test results.
Fertility apps are convenient and a handy way of tracking the basic information in your cycle. They help you stay organised and often feature useful extra information to help with conception and pregnancy.
Clinical studies show that 70% of women don’t ovulate in the middle of their cycle, and you can ovulate at a different time from cycle to cycle, even if your cycles are always the same length [1]. A recent study into several fertility apps concluded 'as a result of the physiological variations of the menstrual cycle length and ovulation day, the fertile window cannot be predicted easily, and it has to be determined during the ongoing cycle. Therefore, to help couples wishing to conceive, apps based on data from previous cycles alone are not suitable to indicate the most fertile days'. Other studies have drawn similar conclusions.[2]
[1] Baird D, McConnaughey D (1995); Lenton EA, Landgren BM (1984a); Lenton EA, Landgren BM (1984b)
[2] Freis A, Freundl-Schütt T (2018); Freundl G, Godehardt E (2003) ; Moglia ML, Nguyen HV (2016); Wise LA, Hatch EE (2015)
Long established in the clinical literature [1], the Basal Body Temperature (BBT) method aims to help detect the date of ovulation in a cycle by taking the basal (lowest) temperature first thing on waking with an oral thermometer, and then charting the change in this daily temperature throughout the month to determine the date of ovulation. It can also be used if you have regular ovulation for predicting the fertile window in the next cycle. Because a rise in temperature is associated with the release of progesterone which occurs during ovulation, a predictable pattern emerges for most women which can help confirm ovulation took place over a number of cycles.
BBT is a relatively cheap and easy way to track your temperatures and a number of apps are now available which combine the idea of a single oral temperature with automatic charting. It is more effective if combined with cervical mucus tracking.
Clinical studies show that 70% of women don’t ovulate in the middle of their cycle, and you can ovulate at a different time from cycle to cycle, even if your cycles are always the same length [2]. As a result because BBT relies on predicting the fertile window based on past cycle data, it's of little practical use if you don't ovulate at the same time each month. With or without an app to help, BBT is unable to help predict ovulation using the current cycle data. Again, even with an app, some users find the charting cumbersome and have difficulty taking a valid measurement each day. Lastly oral thermometers only have an accuracy of around 0.1 degrees Celsius so are not easily able to detect the 0.3 degree rise associated with ovulation with accuracy. Studies assess accuracy for confirmation that ovulation took place at around 69%-83%[3]
[1] Barrett JC Marshall J (1969); McCarthey and Rockette (1983)
[2] Baird D, McConnaughey D (1995); Lenton EA, Landgren BM (1984a); Lenton EA, Landgren BM (1984b)
[3] Freundl G, Godehardt E (2003); Barron M L Fehring R (2005); Bauman JE (1981)
A more modern application of the BBT method is to take several consecutive temperature measurements at various intervals overnight, and then download and interpret these measurements on an app.
As with the BBT method, a skin worn device is a relatively easy way to track your temperatures and it's often more convenient. The devices help establish the pattern of temperature over time, and because of the volume of measurements, they are possibly a little more consistent in detecting ovulation than BBT with an oral thermometer.
Unfortunately measuring temperature at the skin also has some negative aspects - firstly the skin temperature tends to vary in opposition to core temperature changes associated with the release of progesterone, and secondly there is a high chance of 'dropouts' in the temperature signal because it's difficult to maintain contact between the skin and sensor consistently. Just as with BBT, these devices rely on predicting the fertile window based on past cycle data, so they are of little practical use if you are in the 70% of women don't ovulate at the same time each month.[2] They are unable to predict ovulation using current cycle data. At the time of writing there are no papers assessing accuracy of the ability to detect ovulation, but a recent study does identify the 'utility of skin temperature as a retrospective marker for ovulation in 86% of cycles' [3], and a prior paper which shows the ability to identify fertile days with a sensitivity of 78% and an accuracy of 89% [4].
[1] Barrett JC Marshall J (1969); McCarthey and Rockette (1983)
[2] Baird D, McConnaughey D (1995); Lenton EA, Landgren BM (1984a); Lenton EA, Landgren BM (1984b)
Ovulation Predictor Kits (OPKs) provide a positive test for Luteinizing Hormone (LH) using a urine test strip.
LH peaks up to a day in advance of ovulation so OPKs are helpful in providing a short term indication of when you should try and conceive based on your current cycle data. They work well at predicting ovulation for most women that have regular 'middle of the month' ovulation.
OPKs are known to give false positive results for women with PCOS and other ovulatory issues [1]. They sometimes also give false negative results, which can be based on the cutoff point of the test, or simply that the test is not optimised for the natural level of LH for the particular user. OPKs can only provide a snapshot at one point in time in your cycle, meaning you have to use a minimum of two tests a day over a 10-20 range in each cycle to monitor where you are in your cycle. The manufacturers make valid claims for 99% accuracy in detecting LH, but the accuracy estimates for correct advance prediction of ovulation are 70%-84% depending on the publication [2]. OPKs are unable to confirm the date of ovulation or if you haven't ovulated. They are sometimes thought to be messy, impractical and the cost quickly adds up.
Ovulation Prediction Monitors (OPMs) usually allow multiple ovulation predictor urine strip results to be combined to provide a monitoring picture of Luteinizing Hormone (LH) over a cycle. Some monitors use a urine strip that combines LH with E3G - a metabolite that allows assessment of the estradiol level
As with OPKs, as LH peaks up to a day in advance of ovulation an OPM is useful in providing a short term indication of when you should try . The addition of E3G helps provide a fertile window prediction and storing multiple results in the monitor helps with the convenience and monitoring over time compared with OPKs
Just like OPKs, OPMs can give false positive results for women with PCOS and other ovulatory issues [1]. The other drawbacks are much the same as OPKs, and although the monitoring is much improved with an OPM, there remains the issue that they cannot confirm the date of ovulation or tell you if you haven't ovulated. The manufacturers make valid claims for 99% accuracy in detecting LH and E3G (as appropriate), but the accuracy for correct advance prediction of ovulation is likely to be at the top end of the 70%-84% estimates from the publications [2]. Unlike OvuSense, an OPM therfore cannot be used for clinical monitoring as it only provides a picture up to the point of ovulation.
OvuSense is different from anything else you may have heard of, or used previously to monitor your fertility. That's because it measures core body temperature using a specially designed vaginal sensor proven in over 50,000 cycles of use. The vaginal sensor is used overnight only, and data are downloaded to the dedicated OvuSense App each morning. OvuSense provides live updates predicting ovulation up to 24 hours in advance using your current cycle data, then confirming the date of ovulation, all in one device.
By providing core temperature data in real time, throughout each cycle, OvuSense solves the issues variable ovulation causes with monitoring fertility. Even if you have completely regular ovulation, the live prediction with a positive predictive value of 96% [a] and the 99% accurate ovulation confirmation [b] improve your chances of successful conception. OvuSense effectively combines the benefits of OPKs with the benefits of BBT measurement - with the convenience of monitoring in a single device. However, it is more accurate than both methods, going one step further by enabling clinical monitoring in conjunction with the tests offered by your doctor. OvuSense has been clinically proven in 5 key peer reviewed publications [c], [1], [2] which reported on 2 clinical trials. The OvuSense technology also has 8 granted patents [3]
OvuSense provides more accurate results by using a vaginal sensor. Some may find this less convenient than tracking using an external device, but many users report finding the routine of using OvuSense takes the hassle and guesswork out of understanding their cycles. The comfort and ease of use of the sensor was also published clinically [4].
[a] The positive predictive value measures how many of the predicted ovulations OvuSense gets right.
[b] The accuracy measures how many positive and absent ovulations OvuSense confirms correctly.
[c] Note: 4 of the OvuSense publications were clinical posters shown at the annual meetings of the two largest clinical societies for reproductive medicine: ESHRE and ASRM. Poster publications are reviewed by a committee of peers for both societies and only allowed to be presented if deemed of sufficient scientific merit and robustness. They are then published as part of the proceedings of the meetings in the official society journals 'Human Reproduction' and 'Fertility and Sterility', respectively. As is the norm with the development of medical devices, the OvuSense trials were sponsored by the company but the primary authors of the posters are independent clinicians.
[1] The key publication outlining prediction of ovulation was shown at the 2014 ESHRE meeting: Papaioannou S, Delkos D, Pardey J (2014)
[2] The claims for accuracy are based on the data set shown in [1], originally published at the 2013 ASRM meeting as a quality index: Papaioannou S, Aslam M (2013)
[3] US Patents: US8684944, US8496597, US9155522, US9155523, US20190110692; European patents: EP1485690, EP2061380; Chinese patent: CN1650154
[4] The comfort and ease of use of OvuSense were published in the Journal of Obstetrics and Gynecology in 2013, and this survey is repeated annually with our customers with continuous as good or better results: Papaioannou S, Aslam M (2013)
A blood progesterone measurement generally should be obtained approximately one week before the expected onset of the next menses [1] and in a 28 day cycle that's day 21 which is why the test is often called a '21-day progesterone'.
If timed correctly, a blood progestrone is an excellent way of confirming that you have definitely ovulatied in the current cycle. If it is used regularly in successive cycles it can help build up a picture of your ovulation which confirms home testing.
There is a real practical problem if you have irregular cycles or are in the 70% of women who ovulate at a different time in your cycle from the expected ‘norm’[2], or if you just don't have time to get in to have your blood drawn. Given that a false negative test can occur if the timing of your blood draw is out by even a day, a blood progesterone can also lead to the wrong conclusion – potentially setting you on a course of unnecessary treatment.
[1] ASRM (2012) Diagnostic evaluation of the infertile female.; NICE (2004). Fertility Assessment and Treatment of people with fertility problems.
[2] Baird D, McConnaughey D (1995); Lenton EA, Landgren BM (1984a); Lenton EA, Landgren BM (1984b)
3-4 ultrasound 'folliculometry' scans per cycle is the suggested requirement of good cycle monitoring. Your clinician will usually be looking for a dominant follicle (the next one that is most likely to rupture resulting in ovulation) of 20mm or more in size in one of your ovaries. This measurement means that you are likely to ovulate in the next 24-48 hours.
If timed correctly, ultrasound 'folliculmetry' is the accepted gold standard for confirming the likelihood of ovulation in a cycle [1]. It is also essential in assessing the growth and number of follicles, particularly during stimulation of the ovaries, and vital in diagnosis of ovarian issues such as PCOS.
Ultrasound ‘folliculometry’ is not always a good predictor of ovulation, and this isn’t surprising given that it assumes that all women of whatever size and shape, or hormonal make-up will have identically sized follicles just before ovulation occurs. Dominant follicle size can vary greatly [2]. Also, because a scan is a snapshot at one point in time in your cycle, timing the scan correctly is essential, and a number are needed in cycles where the timing of ovulation needs to be known. This is often impractical for the patient and the clinic.
[1] ASRM (2012) Diagnostic evaluation of the infertile female.; NICE (2004). Fertility Assessment and Treatment of people with fertility problems.