The different pregnancy tests: the urine test and the blood test

If a few days after sexual intercourse you experience unusual symptoms, you may be pregnant. These symptoms differ from woman to woman and from pregnancy to pregnancy. In addition, you may have one, several or none of these signs of pregnancy.

The different pregnancy tests

When to carry out a urine pregnancy test?

If a few days after sexual intercourse you experience unusual symptoms, you may be pregnant. These symptoms differ from woman to woman and from pregnancy to pregnancy. In addition, you may have one, several or none of these signs of pregnancy. However, it is very unlikely that you will have all of them. These signs can range from simple fatigue, related to an increase in progesterone levels in the blood, to cramps or abdominal pain.

Here is a non-exhaustive list of other signs of possible pregnancy: mood swings, headaches, more frequent urination, acne flare-ups, sleep problems or increased sensitivity to certain smells.

The most common symptoms indicating the beginning of pregnancy are the absence of menstruation, changes in the breasts (harder, larger and more painful to the touch) and the appearance of nausea or vomiting. If you notice an abnormal change, it is best to take a urine pregnancy test. These tests can be bought in pharmacies and are self-diagnostic tools, i.e. you can use them yourself by following the instructions for use of the device.

How does a urine pregnancy test work?

Unlike the blood pregnancy test, you can buy the urinary pregnancy test in a pharmacy. This test is 99% reliable and measures the level of the chorionic gonadotropin hormone, more commonly known as beta-hCG. This hormone is secreted by the cells of the future placenta after the implantation of the embryo in the uterus. It is detectable 8 to 14 days after fertilisation and this until the end of the pregnancy.

Its rate doubles every 48 hours until the 12th week. It is therefore an excellent marker of pregnancy. It is preferable to carry out this test on the first morning's urine because it is more concentrated in hormones. The device works by fixing the hormones thanks to antibodies placed on a strip.

The strip is either dipped in a container (glass or other) containing the urine or placed directly under the urine stream. After a certain waiting time, indicated on the device's instructions, the device will display a code corresponding to the result "pregnant" / "not pregnant".

You should not interpret a result too long after you have done the test (the delay is specified by the manufacturer). The code varies between devices and may be a colour, line, cross or digital display. The pregnancy test is for single use only. A positive urine test must be confirmed with a blood test.

How does a blood pregnancy test work?

Just like the urine test, the blood pregnancy test measures the level of hCG in the blood. It is 100% reliable and gives you an exact indication of the date of fertilisation and therefore the progress of your pregnancy. A test is negative if the blood hCG level is less than 3 IU/L (international unit per litre).

The absence of detectable HCG makes it possible to rule out an ongoing pregnancy unless the pregnancy is less than 10 days old. A test is positive if the blood hCG level is above 3 IU/L. When the level is between 3 and 10 IU/L, it is preferable to repeat the test a few days after this initial examination to confirm the diagnosis of pregnancy.

The blood test is mandatory and allows you to confirm a pregnancy with your doctor. Indeed, after having obtained a positive response from the medical analysis office, it is imperative to make a first medical appointment with your doctor.In the event of a positive pregnancy test result, a follow-up is offered to all patients either by the adolescent obstetrics and gynaecology unit (UOGA) for patients under the age of 18, or by the obstetrics team for patients 18 years of age and older.H2 Is there an optimal date for a urine or blood test?

For the urine test:

Although the hormone hCG is detectable after the 8th day after fertilisation, the level is so low that it is preferable to wait until the 3rd week of amenorrhoea, i.e. the first week of pregnancy, before carrying out a urine test. This will maximise your chances of obtaining a reliable pregnancy test result.

For the blood test:

As with the urine test, the longer you wait before taking one, the greater your chances of knowing whether or not you are pregnant.You can therefore take a blood test 3 weeks after ovulation, but it is best to wait 4 to 5 weeks after fertilisation.

What are the advantages and disadvantages of the different tests?

The advantages of the urine test:

It is easily accessible (pharmacy or supermarkets), these tests are easy and quick to use and there are low-cost devices available (first prices at 1€). Don't buy your pregnancy test on the internet, they may not correspond to European standards or may be out of date.

Disadvantages of the urine test:

Some tests are more sophisticated than others and will therefore cost more (up to 15€). The urinary test is not reimbursed by Social Security. If the test is done too early, the urine is too diluted, the result is misread or the expiry date has passed, then the test can become a false negative, i.e. you are pregnant but the test has not yet detected any hCG hormones in the urine. Of course, if there are still doubts, for example in the case of irregular menstrual cycles, you can try a test again a few days later.

The advantages of the blood test:

It is 100% reliable. This test is carried out in the presence of health professionals who will advise you on the procedures to follow if you are pregnant. This test is fully reimbursed by Social Security.

Disadvantages of the blood test:

This test is carried out by taking a blood sample. If you are phobic about needlesticks, you may have a very unpleasant time! There are other pregnancy tests such as saliva tests, which are less reliable (98%) and detect the level of beta-hCG in saliva (only available on the internet) or connected tests, which are linked via Bluetooth on your phone and will indicate the result directly on the appropriate application. The application will accompany you throughout your pregnancy with many tips and advice. These tests are of course much more expensive than urine tests (around 20€).

Finally, the last test that can be carried out is an ultrasound scan. An ultrasound can only reveal a pregnancy from three weeks of pregnancy onwards and the embryo observed during a vaginal ultrasound will measure around 1.5mm. However, a blood test can detect a pregnancy earlier than an ultrasound.