Predicting Ovulation

Predicting Ovulation

Efficacy of different methods

by B. Norman Barwin, MD, CM
Summer 2006

Introduction

In the past few years, a variety of luteinizing hormones (LH) urinary ovulation predictor test kits for home use have become available. There are a number of methods for predicting ovulation such as basal body temperature (BBT) charts, cervical mucus changes, Estradiol levels, salivary and vaginal electrical resistance tests and ultrasound measurements of follicular size. However, the measurement of urinary LH concentration is generally accepted as the standard method for predicting impending ovulation. The use of LH kits provides the consumer with a reliable method of ovulation prediction.

Conventional methods of ovulation detection

Basal body temperature charts (BBT).
Prior to the introduction of ovulation predictor tests, the consumer relied on such methods as BBT recordings which are dependant on temperature changes that occur at the time of ovulation. The BBT is recorded over several menstrual cycles in order to demonstrate whether there is a temperature shift of 0.5
^{oC–1.0oC over a period of 24–72 hours. The temperature should be recorded before getting out of bed, preferably after five consecutive hours of sleep, using a thermometer with an expanded temperature scale. Oral or rectal thermometers may be used although digital thermometers are used by many patients, while more recently electronic devices have been introduced. A thermometer probe connected to a microcomputer records and stores the BBT and a light signal indicates different phases of the cycle. Unfortunately, this device is quite expensive and what’s more, BBT does not determine impending ovulation but will show higher temperature after ovulation.}

Cervical mucus.

Saliva tests.

The fern-like structures start to appear 3-4 days before and end 2-3 days after ovulation, the time of maximum fertility. A combination of the dotted and fern-like structures signals the transitional phase, at which time conception is also possible.

Ovulation predictor test kits

Ovulation predictor tests detect the elevation (surge) of LH that precedes ovulation by 12–34 hours and triggers its onset. LH is released from the anterior pituitary gland in 90-minute pulses, peaking at mid-cycle.

These kits are the result of recent advances in monoclonal antibody technology and offer patients a simple and convenient means to identify the pre-ovulatory LH surge in urine. They are more accurate and efficient than traditional methods of identifying the pre-ovulatory period such as BBT graphs, cycle averaging and cervical mucus assessments.

The test works by interpreting a colour change on a test stick, a test pad, or in a test tube. The test stick is covered by a special monoclonal antibody which specifically binds to LH in the urine. In the presence of a special reagent solution, the substrate changes to a blue or pink colour (depending on the kit) in proportion to the amount of LH in the urine sample. By comparing the intensity of the colour change with the control, the onset of the LH surge can be detected.

How do ovulation predictor test kits work?

Simple One Step Procedure.

Easy to Read Results.

Rapid and Convenient.

Accuracy of ovulation predictor tests

For optimal accuracy in identifying the LH surge, twice daily testing is best, offering a 97%–99% predictability of determining the LH surge. Once-a-day testing may fail to identify the LH surge in 5% of ovulating women. This may be due in part to the LH surge lasting less than 24 hours in some cycles. In most clinical situations, testing more than once daily is impractical, unnecessary, costly and inconvenient. Furthermore, there are differences in manufacturers’ recommendations regarding the best time of the day for urine testing. Some tests specifically recommend morning testing, as the first early morning specimen represents the most concentrated urine. Some manufacturers suggest testing between 10 am and 5 pm. to allow for the morning surge of LH to enter the urine, while others advise consistency in the time of daily testing.

A number of drugs such as oral contraceptives, Danazol, Cyclomen, exogenous hCG (LH) and Humegon or Pergonal (hMG), Gonal-F and Puregon may affect the results obtained from ovulation predictor tests. These drugs either reduce the levels of LH or interact with LH. False positive results may be obtained with patients experiencing menopause, premature ovarian failure and Turner Syndrome as well as recent pregnancy or abortion. Temperature variations, albuminuria (protein in the urine) and the consumption of large quantities of fluids prior to testing may also affect the accuracy of the test. Most of the newer generation of LH kits are not influenced by time or temperature.

Clinical application of ovulation predictor tests

Traditional methods of identifying the optimum ovulatory period do not prospectively predict the day of the LH surge and subsequent ovulation. However, the need for precise timing of intercourse may be over-emphasized by patients as well as by physicians treating infertility. Theoretically, sperm can survive up to 48 hours in the female genital tract. Rigid adherence to a specific day of intercourse may inhibit spontaneous intercourse, creating added stress for the couple. More accurate prediction of the day of ovulation with urinary LH predictor tests may alleviate some of this stress. These kits have also been used as a means of birth control in natural family planning, although they are not recommended by any manufacturer for contraceptive purposes.

Timing of insemination

Conception is dependant on the survival of the ovum (egg) for 6–24 hours for fertilization as compared to the sperm. BBT charts and cycle averaging are inaccurate in determining the day of ovulation, requiring multiple inseminations rather than one or two inseminations per cycle. This is not only cost-saving but also more efficient for both the patient and the physician. It remains unclear, however, whether insemination should be performed within a few hours, 12 hours, 24 hours or even later after the detection of the LH surge, and whether this affects pregnancy rates. Precise timing may be more important for intrauterine insemination; however, this has yet to be proven.

Timing of post-coital tests (PCT)

As part of the routine investigation of infertility, the interaction between sperm and the cervical mucus represents the only clinical investigation of sperm transport. Timing is critical, and the PCT should be performed in the immediate pre ovulatory phase when the cervical mucus is maximal and ovulation is imminent. The most common cause of a poor PCT is poor timing. The ovulation predictor kits have an important role to play in the correct timing of PCTs.

Inadequate luteal phase

Traditionally, chronological dating of the endometrium is based on the date of onset of the next menstrual period after biopsy, provided the luteal phase is consistently 14 days long. The detection of the urinary LH surge provides a reference point and allows for a more reliable interpretation of the endometrial biopsy.

In vitro fertilization (IVF) and gamete intra-fallopian transfer (GIFT)

In the case of embryo transfer, embryo donation and transfer of thawed embryos in IVF cycles, twice daily urinary assays may have a part to play for women with normal cycles, although most clinics use medication for cycle regulation. IVF and GIFT programs usually use blood levels of estrogen (Estradiol) and LH as well as ultrasound to determine ovulation.

Conclusion

Although BBT and cervical mucus changes are two fertility awareness methods used traditionally, the advent of monoclonal antibody technology offers patients a simple, reliable and relatively inexpensive method of ovulation prediction. Urinary ovulation LH predictor kits provide a more accurate means of predicting the time of ovulation. Ovulation predictor tests are most useful for timing of optimum fertility to achieve a pregnancy, inseminations, post-coital tests and endometrial biopsies. These tests can be recommended as alternatives to the more cumbersome conventional methods. Studies to determine the value of ovulation predictor kits need to be undertaken and correlated with pregnancy outcome.
The test only needs to be performed for a few days during each cycle and each daily test takes just five minutes to give a result. The test can easily be performed in any setting, whether at home, at a clinic or in a physician’s office.After three minutes, a blue line in the small window shows that the test is complete and has worked correctly. The large (result) window indicates the level of LH in the urine. If the line in the large window is similar to or darker than the line in the small window, the LH surge has been detected, and ovulation should occur in the next 24–36 hours. If there is no line, or if the line is paler than the one in the small window, then the LH surge has not begun and daily testing should continue, each time using a fresh test.All that is required is for the woman to hold the absorbent sampler in her urine stream for 5 seconds.There is evidence to indicate that there are changes in the content of hormones and minerals in the saliva that follow each stage of the cycle. Under a microscope, a sample of saliva shows structures resembling ferns during ovulation, while on all other days shapeless, dotted structures are seen.The cervical mucus has long been used as a good method of ovulation prediction in that characteristic changes occur prior to and following ovulation. Immediately prior to ovulation, the mucus forms a cascade of crystal clear, slippery, egg white-like discharge which stretches into a long thread (Spinnbarkeit). Interpreting the cervical mucus takes instruction. It may be affected by the presence of vaginal infections, intercourse, lubricants or douches. These non-pharmaceutical methods are simple and can be very successful, particularly when combined with BBT. However, they can become tedious and stressful and can interfere with coital performance by placing pressure on the individuals resulting in "tonight is the night" syndrome.

ABOUT THE AUTHOR: Dr. Norman Barwin is the immediate Past President of IAAC. He is the Director of the Braodview Infertility/PMS and Midlife Centre where he established the Andropause Clinic. He teaches the Human Sexuality Course at the University of Ottawa.