Clearblue offers a range of home pregnancy tests, all of which detect the clinically proven urinary pregnancy hormone – human Chorionic Gonadotrophin (hCG) to provide accurate and trusted results in early pregnancy testing.
- Clearblue Pregnancy Test with Weeks Indicator
- Clearblue Digital Ultra Early Pregnancy Test
- Clearblue Digital Early Detection Pregnancy Test
- Clearblue Ultra Early Pregnancy Test
- Clearblue Rapid Detection Pregnancy Test
- Clearblue Flip & Click Pregnancy Test
How hCG is used to detect pregnancy
The hormone hCG is produced in the earliest stages of pregnancy. During early pregnancy it plays a role in survival of the corpus luteum1 and has a significant role in the implantation of the blastocyst and protection of the embryo against immune attack at the foetal/maternal boundary. The pregnancy hormone hCG is initially produced by the embryo and therefore acts as a marker for its presence.2
HCG levels rise rapidly and predictably in the earliest days of pregnancy3 and hCG can be detected in urine 9-10 days following estimated day of conception when using the most sensitive laboratory assays.4 The levels of hCG in early pregnancy have also been found to be highly similar between women.4 This makes hCG an ideal urinary marker for quickly and accurately assessing whether a woman is pregnant or not.
Clearblue Pregnancy Tests can be used up to 6 days before the missed period
Published literature shows that pregnancy hCG levels reach at least 50 milli-International Units per milliliter (mIU/ml) on the day a pregnant woman’s period is due.5-7 If a Clearblue Pregnancy Test is used from the day the period is due, it is more than 99% accurate in detecting pregnancy.8 The high sensitivity of Clearblue Pregnancy Tests means that pregnancy can be detected up to 6 days before the missed period for women who wish to test early. The graph below shows a typical rise in urinary level of hCG from the first detection of pregnancy.
Reference ranges for urinary intact hCG for each day of pregnancy
*From calculated day of ovulation (LH surge +1 day)
Median, 10th and 90th centiles shown. Data from 109 UK volunteers7
Not all pregnant women who test before the day their period is due will obtain a "Pregnant" result.
This is because urinary hCG levels may not yet be above the threshold for the test.
Clearblue Pregnancy Tests are rigorously tested using early pregnancy urine samples from women whose luteinising hormone (LH) surge day is known and from which the day the period is due can be reliably estimated.7 Using these samples it is possible to assess the proportion of pregnant women expected to have sufficient hCG levels in their urine sample to generate a "Pregnant" result, on each day with respect to the day of expected period. If women choose to test early with a Clearblue Pregnancy Test, the likelihood of detecting pregnancy before the day the period is due is clearly displayed on the product packaging. Any woman who tests and gets a ‘Not Pregnant’ result, but still suspects pregnancy, should test again the day the period is due if testing was done early, or 3 days later if the period is overdue.
Over 99% accurate from the day of the expected period
At Clearblue we believe that consumers need a result they can be confident in and act on, and therefore we provide pregnancy test products that deliver over 99% accuracy from the day of the expected period.8
How hCG is used to estimate the time since conception
In order to demonstrate how hCG levels relate to the timing of conception it is important to conduct studies in which the day of conception has been accurately defined. Conception time can be estimated if the LH surge day is known in the cycle in which a woman became pregnant. LH surge is well validated as a marker of impending ovulation, 9-11 and ultrasound studies of follicular rupture have confirmed that the LH surge detected in urine occurs approximately 24-36 hours before ovulation.12 As the egg survives for only around 0.7 of a day, 13 and the fertile period ends on the day of ovulation, 14 conception occurs shortly after ovulation. Therefore detection of the LH surge can be used to estimate the day of conception. Collection of urine samples from complete menstrual cycles in which the volunteer became pregnant and the LH surge is known can demonstrate the utility of hCG in providing an estimate of time since conception.
Following implantation, hCG levels rise exponentially and predictably in blood and urine so hCG has been used to estimate gestational age.15,16 Rigorous trials have shown that there is a consistent pattern to urinary hCG levels in the first few weeks following conception17 such that thresholds for the urinary hCG hormone can be assigned in order to determine time since conception in categories: 1-2, 2-3 and 3+ weeks since conception. These thresholds are employed by the Clearblue Pregnancy Test with Weeks Indicator, so that the test provides not only a ‘Pregnant’/’Not Pregnant’ result, but also an estimate of the time since conception in these week bands.
Furthermore, pregnancy duration estimates using the Clearblue Pregnancy Test with Weeks Indicator result are 97% in agreement with standard of care ultrasound results when ultrasound precision is taken into account.18,19
Digital displays provide more accurate readings
It has been shown that one in four women can misread traditional line pregnancy test results..20 Clearblue Digital Pregnancy Tests contain optical readers which provide clear digital results and eliminates the human error that can occur when reading traditional line pregnancy tests.20
- 1 Baird DD, Weinberg CR, McConnaughey DR, Wilcox AJ. Rescue of the corpus luteum in human pregnancy. Biol Reprod 2003 Feb;68(2):448–56
- 2 Perrier d’Hauterive S, Berndt S, Tsampalas M, Charlet-Renard C, Dubois M, Bourgain C, et al. Dialogue between blastocyst hCG and endometrial LH/hCG receptor: which role in implantation? Gynecol Obstet Invest 2007;64(3):156–60.
- 3 Nepomnaschy PA, Weinberg CR, Wilcox AJ, Baird DD. Urinary hCG patterns during the week following implantation. Hum Reprod 2008 Feb;23(2):271–7.
- 4 Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med 1999 Jun 10;340(23):1796–9.
- 5 Lenton EA, Neal LM, Sulaiman R. Plasma concentrations of human chorionic gonadotrophin from the time of implantation until the second week of pregnancy. Fertil Steril 1982 Jun;37(6):773–8.
- 6 Chard T. Pregnancy tests: a review. Hum Reprod 1992 May;7(5):701–10.
- 7 Gnoth C. and Johnson S. Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments. Geburtshilfe Frauenheilkd 2014;74(7):661–669.
- 8 SPD data on file. Clearblue tests have been shown to be over 99% accurate from the day of the expected period when compared to a reference method in laboratory studies using urine samples supplied for pregnancy testing.
- 9 WHO Temporal relationships between ovulation and defined changes in the concentration of plasma estradiol-17 beta, luteinizing hormone, follicle-stimulating hormone, and progesterone. I. Probit analysis. World Health Organization, Task Force on Methods for the Determination of Fertile Period, Special Programme of Research. Development and Research Training in Human Reproduction. Am J Obstet Gynecol. 1980; 138(4):383-90
- 10 Guida M, Tommasselli GA, Palomba S, Pellicano M, Moccia G, Di Carlo C, Nappi C. Efficacy of methods for determining ovulation in a natural family planning program. Fertil Steril. 1999; 72(5):900-4.
- 11 Gray RH, Simpson JL, Kambic RT, Queenan JT, Mena P, Perez A, Barbato M. Timing of conception and the risk of spontaneous abortion among pregnancies occurring during the use of natural family planning. Am J Obstet Gynecol. 1995; 172(5):1567-72.
- 12 Behre HM, Kuhlage J, Gassner C, Sonntag B, Schem C, Schneider HP, Nieschlag E. 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 Dec;15(12):2478-82
- 13 Ferreira-Poblete A. The probability of conception on different days of the cycle with respect to ovulation: an overview. Adv Contracept. 1997; 13(2-3):83-95.
- 14 Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. Effects of the probability of conception, survival of the pregnancy, and sex of the baby. N Engl J Med. 1995; 333(23):1517-21.
- 15 Rule AH, Michlewitz H, Boyle E, Donahoe M. Use of beta-human chorionic gonadotrophin in gestational aging. Ann Clin Lab Sci. 1985; 15(5):428-34.
- 16 Fritz MA & Guo SM. Doubling time of human chorionic gonadotrophin (hCG) in early pregnancy: relationship to hCG concentration and gestational age. Fertile Steril. 1987; 47(4):584-9.
- 17 Johnson, SR., Miro, F, Barrett, S. & Ellis, JE . Levels of urinary human chorionic gonadotrophin (hCG) following conception and variability of menstrual cycle length in a cohort of women attempting to conceive. Curr Med Res Opin 2009 25: 741–748).
- 18 Johnson S, et al. Accuracy of a home-based device for giving an early estimate of pregnancy duration compared with reference methods. Fertility and Sterility. (2013) 100: 1635–1641.
- 19 Johnson SR. Home pregnancy test compared to standard-of-care ultrasound dating in the assessment of pregnancy duration. Curr Med Res Opin. 2011 2011; 27(2):393-401.
- 20 Tomlinson C, Marshall J, Ellis JE. Comparison of accuracy and certainty of results of six home pregnancy tests available over-the-counter. Curr Med Res Opin 2008 Jun;24(6):1645–9.