Clearblue offers a range of fertility and ovulation products, all of which monitor luteinising hormone (LH) in urine to identify the time of peak fertility. The Clearblue Fertility Monitor also measures E3G (estrone-3-glucuronide) a urinary metabolite of another key hormone, estrogen, to identify the period of high fertility that occurs prior to the LH surge. Monitoring these two hormone levels helps women identify the fertile days of their cycle enabling them to time intercourse to the days when conception is most likely.
How urinary LH and E3G can be used to identify fertile days
There are only a few days per cycle when a woman is fertile and can conceive. Evidence shows that this time of high fertility usually spans 6 days, starting approximately 5 days prior to ovulation and ending on the day of ovulation itself.1 The 6-day fertile period is affected by:
- The lifespan of the egg, which is up to 24 hours after ovulation
- The lifespan of sperm which is more variable. The median is 1.5 days2, but sperm can generally survive for several days in the sperm supportive mucus3 found in the fertile days of the cycle. Sperm survival is therefore dependent on the type and quantity of the mucus within the cervix, and the quality of the sperm itself.
The two most fertile days of this 6-day window are known as peak fertility days. These peak fertility days are the day prior to ovulation and the day on which ovulation takes place4.
Studies show that a surge in LH levels occurs 24-36 hours prior to ovulation4, and that this LH surge is an accurate and reliable marker of impending ovulation5-9. The urinary LH surge pinpoints the two peak fertile days of a woman's cycle, with intercourse on these days being shown to be associated with the highest likelihood of conception1.
In the days leading up to the LH surge, estradiol levels rise gradually, reaching a threshold that triggers the pre-ovulatory LH surge. Tracking the urinary metabolite of estradiol (estrone-3-glucuronide, E3G) allows women to identify the days of high fertility leading up to ovulation, where conception is also possible, and this also gives them advanced notice of their peak fertile days. Data show that women who are aware of their fertile days have an increased likelihood of conceiving10-11.
Furthermore, estradiol stimulates secretion of cervical mucus that is favourable for the survival and transport of sperm. The rise in plasma estradiol corresponds closely to the appearance of sperm-supportive cervical mucus12. Therefore, intercourse during the 6-day fertile period may also lead to conception, as sperm can survive for a number of days.
Typical changes in urinary E3G and LH relative during the menstrual cycle.
The Clearblue Fertility Monitor is a unique innovation proven to increase the chances of conception over the first 2 cycles of use13 which can help reduce the time it takes to conceive14. It accurately monitors levels of LH and E3G to identify two peak fertility days and typically up to 1-5 days of high fertility per cycle prior to a woman's peak fertility. This makes the Clearblue Fertility Monitor the most advanced home method of maximizing the chance of conception.
The innovative Clearblue Digital Ovulation Test range uses a rapid LH 'sandwich' assay to detect the presence of LH in the urine sample. The Clearblue Digital Ovulation Test - 7 Test Pack is 99% accurate in detecting this pre-ovulatory LH surge15 and therefore indicates the two most fertile days. It is a simple home ovulation test kit, which provides easy-to-read, easy-to-understand digital results for greater accuracy in consumers' hands.16
The Clearblue Digital Ovulation Test - 20 Test Pack is more suited for women with irregular cycles, as it includes extra test sticks to give women a greater chance of detecting their peak fertile days17. Data show that over 40% of women experience more than 7 days cycle variability18, and for these women, using the 7 test pack may mean they miss their LH surge if they test on the wrong day. The Clearblue Digital Ovulation Test - 20 Test Pack is very easy to use as the consumer starts testing on day six (or day 12 if a typical cycle is longer than 40 days) and keeps testing each day until her LH surge is detected. Because of these extra test days, the Clearblue Digital Ovulation Test - 20 Test Pack is more than 99% effective in identifying a woman's two best days to conceive naturally, even if her cycles are variable.17
The Clearblue Home Ovulation Test is a traditional ovulation test which is an accurate method to identify the LH surge day and improve a woman's chances of conceiving.
1 Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival
of the pregnancy, and sex of the baby. N Engl J Med 1995 Dec 7;333(23):1517-21.
2 Weinberg CR and Wilcox AJ. A model for estimating the potency and survival of human gametes in vivo. Bio,metrics. 1995 Jun;51(2):405-12.
3 France JT, Graham FM, Gosling L, Hair P, Knox, BS. Characteristics of natural conceptual cycles occurring in a prospective study of sex
preselection: fertility awareness symptoms, hormone levels, sperm survival, and pregnancy outcome. Int J Fertil. 1992 Jul-Aug;37(4):244- 55.
4 Ferreira-Poblete A. The probability of conception on different days of the cycle with respect to ovulation: an overview.
Adv Contracept 1997 Jun;13(2-3):83-95.
5 Corson SL. Self-prediction of ovulation using a urinary luteinizing hormone test. J Reprod Med 1986;31(8 Suppl):760-3.
6 Guida M, Tommaselli GA, Palomba S, Pellicano M, Moccia G, Di Carlo C, et al. Efficacy of methods for determining ovulation in a natural family
planning program. Fertil Steril 1999;72(5):900-4.
7 Behre HM, Kuhlage J, Gassner C, Sonntag B, Schem C, Schneider HP, et al. Prediction of ovulation by urinary hormone measurements with the home
use ClearPlan Fertility Monitor: comparison with transvaginal ultrasound scans and serum hormone measurements. Hum Reprod 2000;15(12):2478-82.
8 Tanabe K, Susumu N, Hand K, Nishii K, Ishikawa I, Nozawa S. Prediction of the potentially fertile period by urinary hormone measurements using
a new home-use monitor: comparison with laboratory hormone analyses. Hum Reprod 2001;16(8):1619-24.
9 Guermandi E, Vegetti W, Bianchi MM, Uglietti A, Ragni G, Crosignani P. Reliability of ovulation tests in infertile women. Obstet Gynecol 2001;97(1):92-6.
10 Hilgers TW, Daly KD, Prebil AM, Hilgers SK. Cumulative pregnancy rates in patients with apparently normal fertility and fertility-focused intercourse.
J Reprod Med 1992 Oct;37(10):864-6.
11 Stanford JB, Dunson DB. Effects of sexual intercourse patterns in time to pregnancy studies. Am J Epidemiol 2007 May 1;165(9):1088-95.
12 Burger, HG. Estradiol: the physiological basis of the fertile period. Int J Gynecol Obstet 1989; Suppl 1:5-9.
13 Robinson JE, Wakelin M, Ellis JE. Increased pregnancy rate with use of Clearblue Easy Fertility Monitor. Fertility and Sterility 2007;87:329-334.
14 Robinson JE, Ellis JE. Mistiming of intercourse as a primary cause of failure to conceive: results of a survey on use of a home-use fertility monitor.
Curr Med Res Opin 2007;23(2):301-6.
15 SPD data on file. Clearblue Digital Ovulation Test has been shown to be 99% accurate when compared to a reference method in laboratory studies using
urine samples from 123 cycles in which the LH surge was identified by a reference method.
16 SPD Data on file. In a study of 72 women reading Ovulation tests typical of normal cycle results, more women obtained the same result as a laboratory
professional when reading the Clearblue Digital Ovulation (CDOT) than reading other leading Ovulation Test brands.
17 Johnson SR, Shaw R. Testing Strategies for the Home Detection of the LH surge. SPD data on file.
18 Creinin MD, Keverline S, Meyn LA. How regular is regular? An analysis of menstrual cycle regularity. Contraception 2004 Oct;70(4):289-92.
