Clearblue Digital Pregnancy Testwith Conception Indicator

The only pregnancy test that can estimate time since conception

Clearblue Professional Series

Accurate - over 99% accurate in detecting pregnancy from the day the period is due

Unique - the ONLY pregnancy test that can estimate time since conception

Clinically proven - correlates with estimation of gestational aging by routine ultrasound

Sensitive - can be used up to 4 days before the period is due

Unmistakably clear - results displayed in words and numbers on a digital screen

Reliable - based on established technology

Simple to use - convenient and easy to interpret

Trustworthy - from Clearblue, the worlds leading brand in home pregnancy and fertility testing

The Clearblue Digital Pregnancy Test with Conception Indicator is:

For more information about the Clearblue Digital Pregnancy Test with Conception Indicator, please visit our websites:

www.clearblue.comwww.swissprecisiondiagnostics.com

SPD Swiss Precision Diagnostics GmbH, 1213 Petit Lancy, Geneva, Switzerland

2011 SPD Swiss Precision Diagnostics GmbH. All rights reserved.

Clearblue is a trade mark Clearblue Professional Series: ROW-CI v1.0 April 2011

Contents

Revolutionising Home Pregnancy Testing 4

Innovation Using Established Technology 5

Solid Clinical Foundations 6

Thorough Scientific Basis 8

State-of-The-Art Micro-Semiquantitation 9

User-friendly and Convenient 11

Boasts a Wealth of Clinical Evidence 12

Reliable in Detecting Pregnancy 13

Highly Sensitive for Pregnancy Detection Before the Day the Period is Due 14

Accurate in Determining Time since Conception 15

Excellent Pregnancy Duration Agreement with Standard-of-Care Ultrasound 16

Conception Result Simple to Interpret 17

Easy to Use 18

Trusted by Women 18

The Test Women Most Favour 19

Meets the Needs of Healthcare Professionals 20

About SPD Swiss Precision Diagnostics GmbH 21

References 22

About Clearblue

Clearblue is the worlds leading brand in home pregnancy and fertility testing.

Consumers trust the Clearblue brand because it delivers the accurate information

they want. The Clearblue product range is built on a strong foundation of peer-

reviewed science and consumer understanding. Clearblue products are also

trusted and recommended by doctors, many of whom recognise that Clearblue is

supported by 25 years of expertise, quality, and innovation in consumer diagnostics.

3

Innovation using established technology As with other home pregnancy tests, the Clearblue Digital Pregnancy Test with Conception Indicator detects

and measures hCG, the hormone produced early in pregnancy and excreted in the urine1

hCG is the marker of choice for detecting pregnancy and has a long and proven history in pregnancy

testing2,3

Pregnancy can be tested either by holding the absorbent sampler of the device in the urine stream for 5

seconds or by dipping the absorbent sampler into urine collected into a clean container, for 20 seconds

The Conception Indicator feature is designed to estimate the time since conception occurred. This estimate

assumes that conception occurred on the day of ovulation, which is defined as the day after the urinary LH

surge

The Conception Indicator feature works on a threshold basis of urinary hCG levels: there are three time

bands that give an estimate of 1-2, 2-3 and 3 or more weeks since conception. These thresholds are based

on extensive research of urinary hCG rise in early pregnancy determined using the day after the LH surge as

a marker for the day of conception

Revolutionising home pregnancy testing

Clearblue Digital Pregnancy Test with Conception Indicator is the latest innovation in pregnancy testing. This simple to use product is unique in that not only does it inform a woman whether she is pregnant or not, but also indicates when she conceived. The test is >99% accurate in detecting pregnancy and 92% accurate in estimating time since conception.

The Clearblue Digital Pregnancy Test with Conception Indicator combines all the benefits of the current

Clearblue one-step digital pregnancy test with the unique advantage of a Conception Indicator feature

Pregnancy is detected with >99% accuracy when testing from the day the period is due

The overall accuracy of the Clearblue Digital Pregnancy Test with Conception Indicator was 92% in

estimating time since conception. This feature uses known levels of human Chorionic Gonadotropin (hCG)

in urine relative to the day of the luteinising hormone (LH) surge +1 day, to estimate time since conception

The accuracy of Clearblue Digital Pregnancy Test with Conception Indicator in estimating time since

conception (and therefore gestational aging) has been further validated by comparison with standard-of-

care ultrasound gestational aging and the results of both methods found to be 98% in agreement

Discovering when conception took place may assist in planning for the pregnancy

The Clearblue Digital Pregnancy Test with Conception Indicator has been developed by SPD Swiss Precision

Diagnostics GmbH (SPD), pioneers of the worlds first one-step and digital pregnancy tests and leaders in

womens health consumer diagnostics

Clearblue has been working closely with consumers and healthcare professionals for over 25 years to

deliver trusted, quality products in pregnancy and fertility

Time since conception [weeks]

hCG level

Average level of hCG

Threshold A

Threshold B

3+ Weeks2-3 Weeks

1-2 Weeks

Figure One: Increasing levels of urinary hCG with time since conception.

4 5

Solid clinical foundationsLH is a hormone produced by the anterior pituitary gland. In females, at the time of menstruation, follicle

stimulating hormone (FSH) initiates the growth of ovarian follicles, specifically affecting the granulosa cells. With

the rise in estrogen levels, LH receptors are also expressed on the maturing follicle that in turn produces an

increasing amount of estradiol. Eventually at the time of the maturation of the follicle, the circulating estrogen

level leads, via the hypothalamic interface, to a release or surge of LH over a 24-48 hour period. This LH

surge triggers the release of the egg (ovulation), and also initiates the conversion of the residual follicle into a

corpus luteum that, in turn, produces progesterone to prepare the endometrium for a possible implantation.

Evidence for using the day after LH surge as the day of conception

1. LH is a marker for ovulation

The World Health Organization (WHO) has defined the rise in circulating LH as the best parameter for

impending ovulation4

Levels of LH in urine correlate 100% with ultrasound detection of ovulation5

A prospective study using the Clearblue Fertility Monitor (formerly the Clearplan Fertility Monitor) found that

in cycles where the two days of peak fertility were detected, (day of LH surge and LH surge +1) ovulation

was confirmed by ultrasound in 91.1% of cycles

2. Conception occurs very shortly after ovulation

Studies have shown that the egg survives for only 0.7 of a day7

Studies have highlighted that the fertile period ends on the day of ovulation8-10

The results of a large, multicentre study demonstrated that conception most likely occurred on the day of

LH surge or day LH+111

Since conception occurs shortly after ovulation, the latter can be used as a proxy for the time of conception12

The time of conception is most likely to occur on the day following the LH surge

% o

f m

axim

um

co

nce

ntr

atio

n

FERTILE PERIOD100

80

60

40

20

0

DAY OF OVULATION

ESTRADIOL

LH

Day of cycle1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Figure Two: Mean changes in the concentration of hormones in peripheral venous plasma (expressed as a percentage of their maximum value relative to the day of the LH surge). Adapted from Collins (1985).13

6 7

Thorough scientific basis Human Chorionic Gonadotropin (hCG) is a peptide hormone produced in pregnancy that is made by the embryo

soon after conception and later by the syncytiotrophoblast (part of the placenta). An important role of hCG is to

prevent the disintegration of the corpus luteum of the ovary and thereby maintain progesterone production that

is critical for a pregnancy in humans.

The Conception Indicator feature uses urinary hCG levels to estimate time since conception.

Evidence for using hCG levels to estimate time since conception Levels of hCG in serum and urine rise rapidly during the first days of pregnancy14,15

In studies absolute levels of hCG have been used to estimate gestational age16,17

Rigorous trials on approximately 3000 individual samples show there is a consistent pattern to urinary hCG

levels during the first three weeks following conception18

The time since conception has been scientifically validated as being related to absolute quantities of hCG

in urine

8 9 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42

4.900

3.700

2.500

1.300

0.100

-1.100

Day relative to LH surge

Log

10 (h

CG

Co

nc +

0.1

0)

Figure Three: Log10 (hCG) levels on the days following the LH surge (mean and 95% confidence interval of the mean shown).18

State-of-the-art micro-semiquantitationInside a Clearblue Digital Pregnancy Test with Conception Indicator

The Clearblue Digital Pregnancy Test with Conception Indicator uses a pioneering new approach and novel

algorithm for measuring urinary hCG

Two strips are contained within the new Clearblue Digital Pregnancy Test with Conception Indicator a low

sensitivity strip and a high sensitivity strip

The Test monitors the Control line which is present on the low sensitivity strip, and the Results lines which

are present on both strips. Only when a valid Control line is detected will the result be determined

The Control and Result lines cannot be read by eye. Instead the test uses an optical system to measure

the density of the lines a red light shines onto the control and result line zones, and the light reflected is

converted into an electrical signal

Its revolutionary micro-semiquantitative technology distinguishes between four different possible results:

(see following page)

8 9

Result line on high sensitivity strip exceeds the

threshold set for 1-2 week result, but not the

threshold set for a 2-3 result

Result line on low sensitivity strip does not

exceed the threshold set for 3+ week result

No hCG detected by the assay strips, therefore

a not-pregnant result is returned

Result line on high sensitivity strip exceeds the

threshold set for 2-3 week result

Result line on low sensitivity strip exceeds the

threshold set for 3+ week result

Result line on high sensitivity strip exceeds the

threshold set for 2-3 week result

Result line on low sensitivity strip does not

exceed the threshold set for 3+ week result

Pregnant and conception occurred approximately 1-2 weeks ago

Pregnant and conception occurred more than 3 weeks ago

Not pregnant result

Pregnant and conception occurred approximately 2-3 weeks ago

User-friendly and convenient The Clearblue Digital Pregnancy Test with Conception Indicator gives the result in words Pregnant or

Not Pregnant providing a much greater degree of clarity than non-digital tests and ease of interpretation

of the test result than with visual tests

If the test result is Pregnant, the Clearblue Digital Pregnancy Test with Conception Indicator uniquely also

displays a result in numbers: 1-2, 2-3 or 3+, indicating that conception occurred approximately 1 to 2

weeks ago, approximately 2 to 3 weeks ago or more than 3 weeks ago

Not pregnant result

Pregnant and conception occurred approximately 2-3 weeks ago

Pregnant and conception occurredapproximately 1-2 weeks ago

Pregnant and conception occurred more than 3 weeks ago

10 11

Boasts a wealth of clinical evidenceNumerous clinical and consumer studies have been conducted to establish the accuracy, reliability and ease of

use of the Clearblue Digital Pregnancy Test with Conception Indicator.

Studies were carried out among untrained healthy volunteer women who were attempting to conceive

Women tested the product at home for some studies or in a study centre for other studies

Studies were carried out in the laboratory using urine samples from women who had conceived, or who

were seeking a pregnancy test

Studies were carried out using urine samples from women who had conceived and then subsequently

obtained their gestational aging by ultrasound.

Highlights of selected studies carried out with the Clearblue Digital Pregnancy Test with Conception Indicator

are given in the next sections of this monograph.

Consumers are informed of how to change weeks since conception to gestational age, using the information

below, which can be found in the product information leaflet. This clear explanation may also help women

understand how pregnancy is dated by healthcare professionals.

How to interpret the results

Results Time since conceptionHow your doctor will date

your pregnancy (based on a 28 day cycle)

Your result is Not Pregnantyou may not be pregnant, or the level of pregnancy hormone may not be high enough to be detected, or you may have miscalculated the day your period was due

Your result is Pregnantand you conceived approximately 1-2 weels ago

3-4 weeks

Your result is Pregnantand you conceived approximately 2-3 weels ago

4-5 weeks

Your result is Pregnantand you conceived more than 3 weeks ago

5+ weeks

Table One: How the Conception Indicator result fits with doctors pregnancy dating (using last menstrual period [LMP]).

Reliable in detecting pregnancy Study Objective: To demonstrate the accuracy of the Clearblue Digital Pregnancy Test with Conception

Indicator

Design: 400 women between the ages of 18 and 45 who were attending a clinic for pregnancy evaluation

provided urine samples quantified for hCG using an extremely sensitive automated method. Expected

Pregnant/Not Pregnant results predicted by the quantitative test were compared to actual results obtained

by trained laboratory technicians using 3 different batches of the Clearblue Digital Pregnancy Test with

Conception Indicator

Results19:

1180/1184 results from the Clearblue Digital Pregnancy Test with Conception Indicator correlated with

results predicted from the quantitative method

The overall accuracy of the Clearblue Digital Pregnancy Test with Conception Indicator in detecting

pregnancy was 99.7%

Table Two: Distribution of results from three different batches of the Clearblue Digital Pregnancy Test with Conception Indicator (combined) compared to results from the quantitative method

Conclusion: The Clearblue Digital Pregnancy Test with Conception Indicator demonstrated over 99%

accuracy in detecting pregnancy when compared to a laboratory method

Results from Clearblue Digital Pregnancy Testwith Conception Indicator

Result expected fromquantitative method

Not pregnant Pregnant Correlation

Not pregnant 820 4 820/824

Pregnant 0 360 360/360

All 820 364 1180/1184

12 13

Highly sensitive for pregnancy detection before the day the period is dueEarly testing for pregnancy (testing before a period is due) can be of value to a woman if she is anxious about

being pregnant, or if she is motivated to take steps to improve her lifestyle as early as possible following

pregnancy.

Study Objective: To demonstrate the sensitivity of the Clearblue Digital Pregnancy Test with Conception

Indicator in the detection of pregnancy on days before the period is due

Design: 89 women who conceived provided first morning urine samples every day during the cycle in

which they became pregnant. Each sample was tested using the Clearblue Digital Pregnancy Test with

Conception Indicator. The day their period should have been due was predicted from the LH surge which

was detected in the samples

Results19:

Conclusion: The Clearblue Digital Pregnancy Test with Conception Indicator is highly sensitive and can

detect pregnancy up to 4 days before the day the period is due.

Pregnancy testing from the day the period is due is >99% accurate. Innovations in the field of pregnancy testing mean that women can test for pregnancy before the day their period is due

The day the period is due requires that a woman remembers the date of her last period and calculates from here, basing this calculation on the expected length of her cycle. However, lengths of menstrual cycles can be variable in women14,19,20 and even taking the mean of the last three cycle lengths does not give an accurate prediction of the length of the current cycle

We recommend that women perform a pregnancy test on the day the period is due. However, as hCG levels rise quickly in early pregnancy, many women can test positive before the day their period is due. If they test negative, but still suspect they are pregnant, women should wait 3 days or until their period is due and test again.

4 3 2 1

100

90

80

70

60

50

40

30

20

10

Days before period

% o

f to

tal

55.0

85.8

96.7 98.3

Figure Four: Number of pregnancies detected with the Clearblue Digital Pregnancy Test with Conception Indicator.

Accurate in determining time since conception Study Objective: To establish the accuracy of the Clearblue Digital Pregnancy Test with Conception

Indicator in determining the time since conception

Design: 89 women who conceived provided first morning urine samples every day for 90 days from the

first day of their period during the cycle in which they became pregnant. Samples from 7 days before

the period was due (7 days post conception) to 28 days after the day the period was due (42 days post

conception) were tested using the Clearblue Digital Pregnancy Test with Conception Indicator. Results of

the Conception Indicator feature were compared to estimated time since conception based on detection of

LH in the urine and taking LH+1 as the day of conception

Results21:

The overall accuracy of the Clearblue Digital Pregnancy Test with Conception Indicator was 92% in

estimating time since conception

The Clearblue Digital Pregnancy Test with Conception Indicator was 96.5% accurate if time since

conception was 1-2 weeks, 76.1% accurate if time since conception was 2-3 weeks and 96.9%

accurate if time since conception was more than 3 weeks

Conclusion: The Conception Indicator feature provides an accurate estimate of time since conception and

is 92% accurate

14 15

Excellent pregnancy duration agreement with standard-of-care ultrasound Study Objective: To determine the level of agreement between the Clearblue Digital Pregnancy Test

with Conception Indicator and standard-of-care ultrasound in assessing pregnancy duration in a real-life,

observational setting encompassing routine clinical care.

Design: Women collected daily urine samples from day one of their next menstrual cycle. If any

volunteer became pregnant, daily urine samples continued to be collected for 43 days after the LH

surge. Samples from day -7 to day +28 relative to the day the period was due (LH surge +15 days)

were tested using the Clearblue Digital Pregnancy Test with Conception Indicator. This categorised any

resulting pregnancies into one of three groups: 12 weeks, 23 weeks, and 3+ weeks since conception.

Information from the standard UK ultrasound dating scan was recorded by their midwife including the

expected delivery date.

Results22: Full data were available from 52 pregnant women who had conceived naturally. The agreement

between the gestational age as calculated by the Clearblue Digital Pregnancy Test with Conception Indicator

result and the exact midwife-recorded gestational age via ultrasound was 82.3%. However, when a 5-day

range was applied to the ultrasound reading (as per routine UK clinical practice), the level of agreement was

98%.

Conclusion: The Clearblue Digital Pregnancy Test with Conception Indicator provides a significantly high

(98%) level of agreement with standard-of-care ultrasound when assessing pregnancy duration in a real-

life, observational setting which closely mirrors daily clinical practice. Conversely, when comparing LMP

only 76.9% of women were found within the +/- 5 day range using ultrasound. Therefore Clearblue Digital

Pregnancy Test with Conception Indicator was more accurate than LMP in dating pregnancy.

Number of samples

Percentage exact agreement

Percentage exact agreement within 5 days of ultrasound dating

95% CI

Agreement with ultrasound age reported by midwife (n= 52)

4,786 82.3% 98% 97.2100%

Table Three: Analysis of Conception Indicator result compared to gestational aging assessment by ultrasound.

Conception result simple to interpret Study Objective: To determine if the Clearblue Digital Pregnancy Test with Conception Indicator digital

display of 1-2, 2-3 or 3+ weeks indicating the time since conception can be correctly read, easily understood

and correctly interpreted

Design: 101 untrained volunteers tested standardised samples of urine containing hCG expected to

produce a Not Pregnant (0 mIU/ml), Pregnant 1-2 weeks (25 mIU/ml), Pregnant 2-3 weeks (200 mIU/ml) and

Pregnant 3+ weeks (20000 mIU/ml) and compared their interpretation of the results with those of trained

coordinators who read the same device

Results21: 384/402 sample results interpreted by the volunteers were the same as those interpreted by the

trained coordinators an overall agreement of 95.5%

Conclusion: The digital result from the Clearblue Pregnancy Test with Conception Indicator is easy to read

and simple to interpret

Not pregnant result

Pregnant and conception occurred approximately 2-3 weeks ago

Pregnant and conception occurredapproximately 1-2 weeks ago

Pregnant and conception occurred more than 3 weeks ago

16 17

76.3%Very Easy

13.1%

4.4%

1.8%

0.0%

4.4%

0.0%Very Difficult

Easy to use 114 consumers completed a questionnaire both at

home and at a study centre on their experiences with

the Clearblue Digital Pregnancy Test with Conception

Indicator. They were asked to indicate whether

they found the instructions for the Clearblue Digital

Pregnancy Test with Conception Indicator very easy,

easy or not easy to understand.

Results21: 99.1% of women found the instructions

very easy or easy to understand.

114 consumers were asked to indicate on a 7-point

scale how easy they found the Clearblue Digital

Pregnancy Test with Conception Indicator to use,

where 1 indicated very easy and 7 indicated very

difficult.

Results21: 93.8% women rated the device at scale

points 1 to 3 for ease of use

Conclusion: The Clearblue Digital Pregnancy

Test with Conception Indicator is easy to use and

understand

Trusted by women114 consumers completed a questionnaire both at

home and at a study centre on their experiences with

the Clearblue Digital Pregnancy Test with Conception

Indicator using a 7-point scale, where 1 indicated very

confident and 7 indicated not very confident in the

test result.

Results21: 93.8% of women rated their confidence

in the result at scale points 1 to 3

Conclusion: Women feel great confidence in

the results obtained with the Clearblue Digital

Pregnancy Test with Conception Indicator

Very Easy 78.9%

Easy 20.2%

Not Easy 0.9%

Very Condent 81.4%

11.5%

0.9%

0.9%

0.0%

Not At All Condent 3.5%1.8%

Not At All Condent 3.5%

The test women most favour114 consumers completed a questionnaire on their experiences with the Clearblue Digital Pregnancy Test with

Conception Indicator and indicated whether they were more likely to buy a pregnancy test kit with a conception

indicator, or less likely to buy one with this feature

Results21:

92.1% (105/114) women said they would be more likely to buy a pregnancy test with a conception

indicator feature than just a standard pregnancy test

93 women provided their own reasons for why they would like a conception indicator: these are shown

in the Table below

92/114 women (80.7%) said they would feel more confidence in a positive pregnancy result if there was

also an indication of when they conceived

Conclusion: A pregnancy test with a conception indicator feature is preferred by women

ReasonsNumber of Volunteers

n (%) [N = 93]

Nice to know when I conceived 50 (43.8%)

Price comparisons are more important 10 (8.7%)

Gives more information 8 (7%)

Appears more accurate/more reassuring 8 (7%)

Speed of test/easy to read 5 (4.3%)

Helps me plan when to see my doctor 2 (1.7%)

Takes anxiety away whilst waiting to see my doctor 3 (2.6%)

Dont know how helpful it is 4 (3.5%)

Other 3 (2.6%)

No response 21 (16.4%)

Table Four: Reasons why women would like a conception indicator feature.

18 19

Meets the needs of healthcare professionals Surveys were carried out among healthcare professionals (obstetricians/gynaecologists, family/general

practitioners, nurse practitioners and midwives) to obtain their perceptions on the usefulness of the

Clearblue Digital Pregnancy Test with Conception Indicator.

Results21:

Opinions expressed included an unmet need for early pregnancy testing and evaluation of hCG

The majority of healthcare professionals were positive about the inclusion of a conception indicator with

a pregnancy test

A high proportion of healthcare professionals considered that the Clearblue Digital Pregnancy Test

with Conception Indicator could lead to some changes in their interaction with patients, open up more

patient dialogue and promote greater awareness of pregnancy in general

Benefits of additional information for patients include:

Planningforthepregnancy

Modifyinglifestyle

Allowingwomentoseekpre-natalcareearlyon

Usefulforgivinganindicationofdeliverydate

Conclusion: Most healthcare professionals felt that the Clearblue Digital Pregnancy Test with Conception

Indicator would be useful to their practice and to their patients

About SPD Swiss Precision Diagnostics GmbHSPD Swiss Precision Diagnostics GmbH is a world leader in the research, design, production and supply

of advanced consumer diagnostic products. Our brands, such as Clearblue and Persona are familiar in

many countries, and are trusted for their accuracy and simplicity by women keen to know more about their

own reproductive health. SPD brands are acclaimed for their pioneering innovation: Clearblue was the first

brand to introduce a one-step pregnancy test, a one-minute test, a urine sample indicator, digitally displayed

results and a Conception Indicator feature.

At SPD, we are committed to helping people make informed decisions about their health and well-being, through

a continuing flow of new and inventive developments. Our research centre is at the sharp edge of innovation,

and is fully engaged in the development of reliable diagnostic products for better health and personal self-care.

If you are a healthcare professional and wish to contact a member of the Clearblue support team about any

product in the Clearblue range, please send an email to spdproductsupport@spdspark.com

Alternatively, you could write to us at:

SPD Swiss Precision Diagnostics GmbH

47 Route de Saint-Georges

1213 Petit Lancy

Geneva

Switzerland

www.swissprecisiondiagnostics.com

20 21

References1. Vaitukaitis JL. Development of the home pregnancy test. Ann N Y Acad Sci. 2004; 1038:220-2

2. Davies S, Byrn F, Cole LA. Human chorionic gonadotropin testing for early pregnancy viability and complications. Clin Lab Med. 2003; 23(2):257-64

3. Stephenson JN. Pregnancy testing and counseling. Pediatr Clin North Am. 1989; 36(3):681-96

4. WHO Temporal relationships between ovulation and defined changes in the concentration of plasma estradiol-17 beta, luteinizing hor-mone, follicle stimulating hormone, and progesterone. I. Probit analysis. World Health Organization, Task Force on Methods for the Deter-mination of the Fertile Period, Special Programme of Research, Development and Research Training in Human Reproduction. Am J Obstet Gynecol. 1980; 138(4):383-90

5. Guida M, Tommaselli 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

6. Behre HM, Kuhlage J, Gassner C, Sonntag B, Schem C, Schneider HP, Nieschlag E. Prediction of ovulation by urinary hormone measure-ments with the home use ClearPlan Fertility Monitor: comparison with transvaginal ultrasound scans and serum hormone measurements. Hum Reprod. 2000; 15(12):2478-82

7. 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

8. 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; 333(23):1517-21

9. Dunson DB, Baird DD, Wilcox AJ, Weinberg CR. Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation. Hum Reprod. 1999; 14(7):1835-9

10. Keulers MJ, Hamilton CJ, Franx A, Evers JL, Bots RS. The length of the fertile window is associated with the chance of spontaneously conceiving an ongoing pregnancy in subfertile couples. Hum Reprod. 2007; 22(6):1652-6

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. Lynch CD, Jackson LW, Buck Louis GM. Estimation of the day-specific probabilities of conception: current state of the knowledge and the relevance for epidemiological research. Paediatr Perinat Epidemiol. 2006 Nov;20 Suppl 1:3-12

13. Collins WP. Hormonal indices of ovulation and the fertile period. Advances in Contraception 1985;1:279-294

14. Nepomnaschy PA, Weinberg CR, Wilcox AJ, Baird DD. Urinary hCG patterns during the week following implantation. Hum Reprod. 2008; 23(2):271-7

15. Zegers-Hochschild F, Altieri E, Fabres C, Fernndez E, Mackenna A, Orihuela P. Predictive value of human chorionic gonadotrophin in the outcome of early pregnancy after in-vitro fertilization and spontaneous conception. Hum Reprod. 1994; 9(8):1550-5

16. Rule AH, Michlewitz H, Boyle E, Donahoe M. Use of beta-human chorionic gonadotropin in gestational aging. Ann Clin Lab Sci. 1985; 15(5):428-34

17. Fritz MA, Guo SM. Doubling time of human chorionic gonadotropin (hCG) in early normal pregnancy: relationship to hCG concentration and gestational age. Fertil Steril. 1987; 47(4):584-9

18. 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 Mar; 25(3):741-8

19. Pike J, Ellis J, Johnson S, Shaw R, Parkinson P, Perry P. Accuracy of new Clearblue Digital Pregnancy Test with Conception Indicator. Hum Reprod 2010; 25(suppl 1):i169-170

20. Cole LA, Ladner DG, Byrn FW. The normal variabilities of the menstrual cycle. Fertil Steril. 2008 Apr 21. [Epub ahead of print]

21. Data on file

22. Johnson S et al. Agreement between the Clearblue Digital Pregnancy Test Conception Indicator and standard-of-care ultrasound dating in the assessment of pregnancy duration. Curr Med Res Opin 2011. In Press

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