Available without a prescription and not reimbursed, pregnancy tests are sold in pharmacies and, since 2014, in medium and large surfaces. For a few euros and in a few minutes, they allow you to know quite reliably if you are pregnant or not.

The pregnancy test is based on the detection of the hormone HCG (chorionic gonadotropin hormone) in the urine. This hormone is secreted after implantation of the fertilized oocyte duringovulation, in the lining of the uterus (approximately 7 days after fertilization). For three months, it will keep the corpus luteum active, which secretes progesterone and estrogen, two hormones essential for the proper development of pregnancy. HCG is therefore only present in pregnant women, hence its nickname “pregnancy hormone”.

If the pregnancy test is positive, the pregnant woman should contact her doctor so that the latter can prescribe a blood pregnancy test and thus confirm the diagnosis definitively.

Most tests promise effectiveness from the first day of late period. However, testing too early increases the risk of a “false negative”. Indeed, the test reacts positively from a certain level of HCG, however, this rate is calculated on the basis of a cycle of 28 days with an ovulation on the 14th day. If cycles are longer or ovulation is later, fertilization occurs later. The HCG hormone level is therefore lower on the first day of a missed period and may therefore go undetected (1). Conversely, it is advisable not to delay too long to take a pregnancy test because it is important to know your condition as soon as possible in order to avoid potentially harmful behaviors for the development of the fetus. Waiting 6 to 8 days of late period seems a good compromise to have a reliable result.

A pregnancy test costs on average 5,19 €, but the prices vary from 0,59 € (test strip type) to 14,50 € (digital test indicating the age of pregnancy) (2). However, the price is by no means an indication of reliability. It plays more on the comfort of reading and use (example of brands: Clearblue, Predictor, etc …)

It is sensitivity to the hormone HCG which is a guarantee of reliability. However, all current tests show a threshold of 20 UI/ l to 25 UI/ l, threshold ensuring a reliable result if it is positive. To verify this, the Medicines Agency (MSNA) carries out spot checks. The latest in date (3) confirm the reliability of these tests when they indicate a positive result. 

However, on condition that you follow the instructions for use. Some so-called early tests promise effectiveness 4 days before the estimated period due to higher sensitivity (10 to 12,5 UI/ l), but their reliability is lower, especially due to variations in ovulation date and hormone levels HCG according to women. Be careful also with the tests sold on Internet : they can come from uncontrolled laboratories, their reliability is not guaranteed. 

In France, it was in 1973 that pregnancy tests were put on sale. If the principle remained the same – detecting the hormone HCG in the urine – on the other hand, it was necessary to play the apprentice chemist by mixing different compounds in different test tubes, to wait several hours before viewing the result in reflection … in a mirror!