The urine pregnancy test, available without a prescription in pharmacies, drugstores and supermarkets, is a reliable way to confirm pregnancy in the event of a late period. You still have to use it correctly and not be too impatient.

The pregnancy test is based on the detection of the hormone beta-hCG in the urine. Thanks to an immunological process, certain antibodies will react in the presence of this hormone.

The beta-hCG hormone is secreted by the corpus luteum upon implantation of the egg, approximately 7 days after fertilization. A hormone specific to pregnant women, its presence in the urine therefore indicates the existence of a pregnancy.

Most pregnancy tests can be done on the first day of your period. However, it is advisable to wait several days late – at least 2 or 3 days – in order to limit the risk of “false negative” due to a test carried out too early. Indeed, the test reacts from a certain level of beta-hCG, but this rate is calculated on the basis of a standard cycle of 28 days with ovulation on the 14th day. In case of longer cycles or late ovulation, fertilization takes place later. The level of beta-hCG will therefore be logically lower on the first day of the delay of the rules and thus risks not being detected by the pregnancy test (1).

Some so-called early tests promise efficacy 4 days – or even 6 days – before the due date of menstruation thanks to a higher sensitivity to the beta-hCG hormone (10 to 12,5 IU / l against 20 IU / l at 25 IU / l for classic tests). However, due to variations in ovulation date and beta-hCG hormone levels among women, these tests are not always very reliable. Moreover, on their instructions for use, these predictive tests do not promise 99% reliability (as is the case for other tests) when they are performed before the expected date of the rules.

It is therefore better to wait a few days of late period to obtain a reliable result and avoid the disappointment of a “false negative”.

Pregnancy tests are easy to use. They come in the form of a plastic stick (more rarely a strip), one of the tips of which is to be placed under a stream of urine for a few seconds.

After a few minutes (3 on average), the result will appear in different modalities depending on the test used:

• in the form of a colored line indicating the presence of pregnancy;
• a little extra;
• with the word “pregnant” in full for digital tests;
• for some models with the word “pregnant” and the number of weeks since conception (“1-2”, “2-3” or “3+”).

Most pregnancy tests have a so-called “test” window that allows you to confirm that the test was done correctly. If no marker appears in this test window, the test has been misused, and its result is therefore not valid. It is then advisable to redo another test, new of course, because pregnancy tests are for single use. Once used, they are no longer effective.

Note that some medicines can falsify the result of the pregnancy test. This is particularly the case with ovulation inducers containing the hormone beta-hCG. If the test is taken too soon after their administration, they can induce a false positive (the test indicates pregnancy when there is not).

It is indeed advisable to do the test on the urine in the morning, on an empty stomach. As the first urine is more concentrated, the level of beta-hCG will be higher and therefore more easily detectable by the test, especially if the pregnancy is recent.

Although most tests promise 99% effectiveness from the first day of your period, and for some even 4-6 days before your period is due, it is advisable to be a little patient and wait a few days. late period before taking a pregnancy test. The longer the period is delayed, the higher the beta-hCG level will be and therefore easily detectable, especially since it increases very rapidly during the first days of pregnancy. Taking your test between 3 and 8 days after the first day of the late period seems a good compromise: this makes it possible to avoid a false negative due to a test carried out too early and to know your pregnancy sufficiently early and thus to avoid behavior at risk in early pregnancy (alcohol consumption, taking certain medications, etc.).

Of course, there is no point in taking a pregnancy test after unprotected sex. At this stage, there is no secretion of beta-hCG hormone yet, so pregnancy is not detectable.

If the pregnancy test is negative but the period still does not come, it is advisable to take a pregnancy test again a few days later.