What is an Ovulation Predictor?

feb 22, 2022 | 2 Minutes Leer

Ovulation prediction kits are now widely available and reasonably inexpensive, so they have become popular with many women planning for conception and pregnancy.

There are 3 main types of ovulation predictors.

There are two types of tests that are used at home. The most common and easiest to use is a urine test called an ovulation prediction kit (OPK), while the second type, a saliva ovulation test, uses a special microscope to detect a hormonal change in saliva. The third type of ovulation predictor is a series of blood tests, which you may decide to arrange through your doctor if you are having trouble identifying your fertile period.

What does an ovulation predictor measure?

Just before ovulation occurs, there is a significant rise in the level of certain hormones, including estrogen and luteinizing hormone (LH). The advantage that an ovulation predictor test has over some of the other methods of measuring ovulation is that it can detect the rise in hormones that occur in the lead up to ovulation.

Using the rise in your basal body temperature that occurs after ovulation as a measure of ovulation will only give you information after you have ovulated.

Little of your body’s fertile time remains after ovulation. The ovulation temperature technique is only useful if you are trying to chart a pattern of ovulation over a number of months. However, an ovulation predictor will often give a result between one and two days before ovulation, so theoretically, you are able to ensure that intercourse occurs at your most fertile time.

How accurate is an ovulation predictor?

There is very solid research behind everyday ovulation prediction kits. Advances in medical technology have made these kits easier and cheaper to manufacture and therefore widely available.

However, one of the drawbacks of an ovulation predictor is that the rise in hormone levels may occur several times before the egg is released.

It is reasonably common for an ovulation predictor to give a “false positive” result. The result, while accurately reflecting the presence of a high level of hormones, does not necessarily mean that ovulation has occurred.

Urine tests and ovulation predictor kits

An ovulation predictor kit (OPK) operates in a very similar way to a home pregnancy test. These kits test for the presence of luteinizing hormone (LH) in the urine, which occurs between 24 and 48 hours before the release of the egg.

While each kit may have a slightly different methodology, the kits usually require you to use them daily. Generally, the first thing in the morning is best for around a week at the time that you estimate will be your most fertile time.

Ironically, women who have irregular cycles and therefore are most likely to need to use an OPK to assist them to predict the time of ovulation usually find the kit is less accurate to use because of the variability in their fertile period.

One solution offered by OPK manufacturers for those with irregular cycles is to use the kit more frequently throughout the cycle. However, this is a more costly option. Most kits supply between 5 and 12 individual tests. It is possible to buy the tests in bulk in some places.

Saliva ovulation tests

Another hormone which increases just before ovulation is estrogen. The presence of estrogen causes a slight change in the structure of saliva which involves an increase in its salt content.

This increase in salt in saliva because of higher levels of estrogen can be detected quite easily under a microscope. The salt-laden saliva crystallizes into a fern-like pattern when it dries, unlike the usual shapeless and dotted pattern that saliva usually dries into.

Saliva ferning can be identified from around 4 days before ovulation and is also present for about 2 days after ovulation. For this reason, it is important to test daily during the first part of the woman’s cycle.

Although most optical microscopes at the correct setting could theoretically detect this pattern, unless you have expertise with the use of microscopes, it is probably worth investing in a special mini microscope designed to detect saliva patterns.

The saliva ovulation predictor test requires the user to develop a certain level of familiarity with patterns of saliva and can be a little tricky. However, although there is an initial investment in the purchase of the device, there are no ongoing costs, so this can be quite an economical way of identifying your fertile period.

Blood tests and ovulation

Regular blood tests taken every few days during your cycle can give more accurate measures of the quantity of hormones present at different stages of your cycle.

These tests are usually organized through your primary care provider or a fertility specialist.

Because they are more invasive than testing urine or saliva, blood tests are not normally be done unless other methods of identifying ovulation had been attempted first.

There are a number of conditions, some easily treated, which can interfere with fertility because your body is not producing the appropriate amounts of hormones at certain stages of your cycle.

Issues such as thyroid or endocrine problems (such as polycystic ovary syndrome, which affects between 5 and 12% of women and is one of the leading known causes of infertility) can be treated using drugs to stimulate ovulation. It’s important to get tests to confirm an accurate diagnosis of any condition before undergoing treatment.

The information of this article has been reviewed by nursing experts of the Association of Women’s Health, Obstetric, & Neonatal Nurses (AWHONN). The content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment. For more advice from AWHONN nurses, visit Healthy Mom&Baby at health4mom.org.