DETERMINING FERTILITY: The Ovulation Kit and Cervical Mucus Characteristics

Couples considering having a baby can utilize a home ovulation test kit supplied from a pharmacy in order to pinpoint the best time to conceive a child. The most fertile time for a woman is usually the first two weeks before her menses begin. At this time, the pituitary gland begins increasing production of luteinizing hormone, which then stimulates one of the ovaries to release an egg within one to two days.1 This process, known as ovulation, is the time when the greatest chances of getting pregnant occur.

Ovulation prediction kits are designed to measure a woman’s urine for traces of a hormone that signifies the impending release of an egg from the ovaries. The use of the kit allows couples who are trying to conceive to know which days the woman is most fertile, which are usually the day preceding and that of ovulation. Typically, a woman ovulates between the 12th and 14th days of the menstrual cycle, with the 1st day being day one of the menses. The majority of test kits detect the surge of luteinizing hormone that occurs 24 to 36 hours prior to actual ovulation.2 Testing should begin 2-3 days prior to when a woman expects to ovulate based on her previous 3-4 menstrual cycles in order to account for her most fertile days.

Directions for using an ovulation kit differ based on the specific kit one is using. Most of these kits require that a test stick be held in the urine stream to measure hormone levels, or the use of urine test strips that can be inserted in a reusable monitor. Some tests provide relatively instantaneous results while others may take up to an hour, and some tests use a colorization process to indicate levels of luteinizing hormone in the urine. The more darkly stained a test strip is, the more luteinizing hormone present in the urine, and the closer to ovulation a woman is.

Testing each day in the 5 days prior to and 5 days after predicted ovulation is important. If a normal cycle is 28 days, then testing should begin on day 10 and continue until day 20. Once the test strips have reached their darkest color, this signifies that production of luteinizing hormone has reached its peak and ovulation will occur in the next two days. Testing each day at the same time will provide the most accurate results, however the specific time of day (morning, afternoon, evening) is not important as long as the same time each day is adhered to.

To provide the most accurate measurement, a woman should avoid drinking large amounts of fluids 3-4 hours preceding the test to avoid diluting the measurable amount of hormone. Also, avoiding urination (as best as possible) in the 1-2 hours prior to measurement will also allow for a more concentrated sample. If a woman has taken birth control pills and recently discontinued them, she should wait one to two months in order for her cycles to become regular again. Compared to using ultrasound in the diagnosis of ovulation, urine measurement of luteinizing hormone correlated 100% with that method,3 demonstrating the effectiveness of measuring urine hormone levels.


Inconclusive results from the ovulation kit can mean one of several things: it was not used properly, testing was begun either too late or too early in the cycle, or the woman did not ovulate. Falsely positive readings may show high levels of luteinizing hormone without ovulation. This can occur from the effects of certain medications or health conditions such as ovarian cysts. If the test fails to register luteinizing hormone or if using the kit for 3 months without success, a physician should be consulted in order to explore other reasons for not conceiving including the male partner.

Cervical Mucus Ferning

Another simple way to determine fertility involves examining the cervical mucus. The phenomenon of mucus ferning has been observed for some time now, and is a reliable indicator for determining fertility.4 The mucus secreted from the cervix changes throughout the menstrual cycle according to where a woman is along the hormonal continuum. Simply put, a small sample of cervical mucus can be examined on a microscope slide and observed for a specific pattern once it dries out. This pattern resembles that of a fern leaf, which signifies a fertile period due to the effects of hormones on the mucus. The mucus will fern because of the effects of estrogen on the fluids of the body. Increased amounts of electrolytes are secreted into a woman’s bodily fluids, leading certain fluids to dry in a fernlike pattern. Among these is cervical mucus as well as saliva; both will exhibit this unique pattern of drying.

A woman’s hormonal cycle alternates between times of high estrogen and times of high progesterone. The time prior to ovulation is characterized by high estrogen and after ovulation; both progesterone and estrogen are secreted from an area of the ovary known as the corpus luteum. The relative amount of hormone affects the mucus that is secreted from the cervix. During ovulation, the mucus is secreted in large amounts and is clear. It can be drawn out into a fine thread, and has the quality of raw egg white. When mucus appears this way, it is known as spinnbarkheit. Ovulatory mucus can be drawn out to at least 6 centimeters, and has a pH of 6.5 or less, and will fern when dried on a microscopy slide.

The peaking of estrogen levels just before ovulation causes the cervical mucus to become thinner and capable of ferning.5 This mucus contains greater than 95% water and is thin, clear, and copious. Thicker mucus is attributed to the presence of progesterone produced by the corpus luteum and will not fern when placed on a microscopy slide. This mucus is characteristic of the time period following ovulation; it becomes more thick and rubbery from the effects of the progesterone, and will appear in small clumps when viewed under a microscope. Persistent ferning throughout the menstrual cycle suggests anovulatory cycles (menstrual cycles when no eggs are produced by the ovaries) or insufficient progesterone secretion. Several products are available for a couple that is trying to conceive that allow them to determine ferning patterns in cervical mucus. Many are reusable, and some are available as small viewing devices that are no larger than a tube of lipstick.


Both urine hormone testing and cervical mucus ferning provide reliable information regarding a woman’s ovulatory status. Each one has it’s own measure of reliability, and it is important to know that both are not absolute guarantees of ovulation, or that conception will take place during the demonstration of these signs. However, when both methods are utilized, a couple stands a much better chance at determining when the most optimal times for procreation are.

1 Wang XX, Wu ZY. Prediction of ovulation Zhonghua Fu Chan Ke Za Zhi. 1990 Mar;25(2):86-8, 124.

2 Handbook of Nonprescription Drugs. American Pharmaceutical Association, 1996. ClearPlan Easy Fertility Monitor ProductInformation. Unipath Diagnostics Company.

3 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 Nov;72(5):900-4.

4 Campo S, Garcea N. The canalization of cervical mucus in the human fertility. Acta Eur Fertil. 1991 Jan-Feb;22(1):37-42.

5 Garcea N, Giacchi E, Campo S, Messina M, Panetta V, Moneta E. Canalization of human cervical mucus. Obstet Gynecol. 1984 Aug;64(2):164-9.