To optimize your chances of pregnancy, it is important to know your ovulation date in order to identify your period of maximum fertility. Among the different methods used to detect this key fertility day, ovulation tests appear to be the most reliable.

The ovulation test is a test to detect the date of ovulation, an important parameter to know to optimize your chances of pregnancy or when pregnancy is delayed. In each cycle, the woman is in fact fertile only for a few days: 3-4 days before ovulation and the day of ovulation. Determining your ovulation date therefore makes it possible to identify your period of maximum fertility, or fertilization window, and to schedule sexual intercourse at the right time.

Over-the-counter in pharmacies and on the internet, these tests are in the form of strips or sticks on which the woman places a few drops of urine, preferably at the same time of the day. If there has been no nighttime urination, the morning urine test should be avoided. Very concentrated, they could give a false positive.

The test will consist in detecting, in this urine sample, the luteinizing hormone (LH) and more precisely the LH surge. This hormone is produced in greater quantities 24 to 36 hours before ovulation: from less than 10 IU / ml at the start of the cycle to almost 70 IU / ml at the time of the ovulatory peak, it is this rise in LH which will trigger ovulation.

It is not necessary to take an ovulation test every day of the cycle; it is unnecessary and it would be costly. To choose when to start using the test, doctors recommend subtracting 16 to 18 days from the cycle length. For a 28-day cycle, we will start the tests on the 10th day (28-18), or 10 days after the start of the rules. If no ovulation has been detected after 10 days of testing, it is advisable to repeat the tests in the next cycle starting two days earlier (1).

In the case of variable cycles, it is best to take the shorter one and start testing earlier so as not to miss ovulation. If the cycles are very long (more than 40 days), very short (less than 22 days) or irregular, it is recommended to use another method, such as the temperature curve to verify in the first place that there is well ovulating (2).

When the test is positive – that is to say when it has detected a rise in LH – a small colored bar or a smiley (on a digital screen) appears depending on the model. This means that ovulation will take place 24 to 48 hours later. So now is the perfect time to schedule sex to get pregnant.

If after three months of ovulation tests, no ovulation has ever been detected, it is advisable to consult for additional examinations to diagnose and manage any dysovulation (poor quality ovulation) or anovulation ( absence of ovulation).

Easy to use, ovulation tests have the main advantage of being predictive: they allow you to know the date of ovulation 24 to 48 hours in advance – and therefore to schedule sexual intercourse accordingly – at the difference from the temperature curve method, which only detects the ovulation period afterwards, that is to say once ovulation has passed and therefore the fertility period has ended.

The detection threshold for urinary LH varies from one brand to another, with a sensitivity ranging from 25 to 40 mIU / ml depending on the model. Brands announce a 98 to 99% reliability rate… in detecting the LH surge, not in achieving pregnancy. Indeed, the technical reliability of the ovulation test does not guarantee the occurrence of pregnancy. As a reminder, a young couple, without fertility problem, has only a 15 to 20% chance of pregnancy even after having had sex at the best time of the cycle.

Certain parameters can interfere with the results and give “false positives”: hormonal treatment (ovulation inducer in particular), ectopic pregnancy, ovarian cyst, polycystic ovary syndrome, premature ovarian failure, hypothyroidism ( 3).

Ovulation tests are still the most reliable method compared to natural methods of temperature curve and observation of cervical mucus.