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Pregnancy tests—when and how to use them

Pregnancy is often a happy, welcome, longed-for event, but discovering an unplanned pregnancy can be a shock! Symptoms such as nausea, fatigue, and increased appetite are early indicators of pregnancy but, if done correctly and at the right time, a simple home pregnancy test can tell you what you want to know.

Pregnancy tests are widely available and easy to use—just a few drops of urine are needed to get a result. However, they are not 100% reliable, so it is best to consult your doctor or gynaecologist if you think you might be pregnant. Then you can get the information you need to decide what to do next.

Am I pregnant?

A woman can only become pregnant (conceive a child) under certain, very specific conditions. Around day 14 of an average 28-day menstrual cycle, a woman ovulates; that is, she releases an egg from one of her ovaries, which travels into the Fallopian tube and makes its way toward the uterus. If sperm enter the vagina and make their way through the uterus and into the Fallopian tubes, the sperm that survive the journey have the opportunity to fertilize an egg, if it is present there at the same time.

It is important to remember that the length of even the most stable cycle can vary and the timing of ovulation can change from month to month. This is especially true for teenagers whose bodily rhythms are still volatile and variable. This is an excellent reason to track your period. It gives you information about the duration of your cycle and makes it much easier to notice changes such as delayed periods or unusual bleeding in between periods.

The window of opportunity to fertilize an egg lasts about 12 to 24. However, sperm can survive in a woman’s body for several days, so the duration of sperm viability is much longer. If sperm is already present (because of sexual intercourse in the previous few days) when a woman ovulates, her egg could be fertilized. Or, if a woman has sex while she is ovulating, the sperm could immediately fertilize an egg that has just been released.

It doesn’t matter if it’s the first, fifth, or hundredth time a woman has sex—wanting or not wanting to become pregnant is irrelevant. The human body is designed for sexual reproduction.


If an egg meets a healthy, fertile sperm, it can be fertilized, and so mark the beginning of pregnancy.

A woman may not be able to conceive with one male partner but may be able to with another; some couples spend years trying to get pregnant, while for others it happens right away.

How could this happen?!?!

The safest way for sexually active people to avoid pregnancy is to use contraception. Ask your doctor to recommend the most suitable method for you. But remember, not all types of contraception protect against STDs, so be sure to use a condom unless you are in a committed, exclusive relationship and both parties are sure they are free from disease.

Yet, life is unpredictable, and people are not always careful and wise—especially when it comes to love and passion.

After a wild party, a heady night out, or a romantic date, women have been known to anticipate their next period with trepidation because contraception was the last thing she was thinking about in the heat of the moment or perhaps because it felt inappropriate or embarrassing to discuss in a moment of new intimacy…


Unplanned pregnancy can also happen in cases of rape or sexual assault, when a woman is even less likely to be protected by effective contraception.

And sometimes, even if a couple is using contraception, it just doesn’t work. In such cases, a woman may consider using emergency contraception, also called ‘the morning after pill’.


How a pregnancy test works

The most accurate method of confirming pregnancy is a blood test done in a laboratory, but this takes time—sometimes several days—and it may be difficult to wait. Home pregnancy tests are sold over the counter in most pharmacies and can often be found in supermarkets and drugstores. These provide results much more quickly but are less accurate.

A pregnancy test detects the presence of a hormone—human chorionic gonadotropin or hCG—in a woman’s blood or urine. Once an egg is fertilized and has implanted itself in the wall of the uterus, the developing embryo will begin producing hCG.

This hormone signals the body to secrete another hormone, progesterone, which serves to maintain and build the endometrial lining of the womb to accommodate the embryo.

Now, take a breath. There is no point in taking a pregnancy test immediately after unprotected sex. If one of your eggs has been fertilized, it will take 6–7 days for that fertilized egg (which has already begun to cleave and develop) to travel through your Fallopian tube and reach the uterus, where it must implant itself into the endometrium or uterine lining.

At the earliest, levels of hCG will be high enough for detection by a laboratory blood test about 10 days after fertilization but won’t yet be detectable in the urine.


You are most likely to get an accurate result if you take a home pregnancy test after the first day of your missed period.

From this point, levels of hCG increase rapidly reaching the maximum at around 7¬–12 weeks of pregnancy. After this hCG production begins to taper off but can still be detected in a woman’s blood and urine throughout her pregnancy.

If a woman has a miscarriage or an abortion, it takes the body several weeks to reset and hCG will be present, so testing for a new pregnancy during this period is very difficult.

How do I use it?

Home pregnancy tests are really easy to use. Although they all work according to the same principle, they do come in several different types, so be sure to read the instructions before you begin and check the expiry date! A home pregnancy test usually consists of a reactive test strip encased in plastic. Some require that you position the end of test strip directly under the stream of urine for a few seconds, while others provide a pipette. The result will appear in a few minutes’ time but can be shown in different ways depending on the test used.


The newest home pregnancy tests can even estimate how far along you are!

The test strip for a home pregnancy test is divided into zones—the sample pad, the reaction zone, the test zone, and the control zone. The urine sample is deposited onto the sample pad and then seeps into the reaction zone where any hCG in the urine binds to antibodies that contain an enzyme, which participates in a colour reaction in the next two zones. The urine continues to seep into the test zone where the enzyme-linked antibodies catalyse a colour reaction (usually a line or a small cross) if hCG is present. Finally, the urine seeps into the control zone where another colour reaction (another line or cross) indicates the test has been carried out correctly. One colour reaction indicates a negative test result, or no pregnancy. Two colour reactions indicate a positive test result—you are pregnant.

Most home pregnancy tests can be used at any time of day, but the concentration of hCG in the urine is higher first thing in the morning. Your test result will be more reliable with your first morning pee if you are able to wait!


Is it 100% accurate?

The main advantage of home pregnancy tests is that provide rapid results; however, they are not 100% accurate.

You may get a false positive if:

  • the test you are using has expired
  • you are using fertility drugs or other medications that contain hCG
  • you are suffering from liver disease, cancer, or some other illness that produces elevated levels of hCG


An ectopic pregnancy, problems with the ovaries, or menopause hormones can also cause inaccurate test results.

You might get a false negative if:

  • you are impatient and take the test before hCG can be detected
  • you rush to read the result without waiting long enough for the reaction to occur 
  • the urine used for the test was diluted for some reason and the hCG doesn’t register

The general recommendation is that you repeat the home pregnancy test in two weeks.  If you get another positive result, you can ask your doctor for a blood test. This method is considered to provide the most reliable results.

What happens next?


Regardless of the test result, make an appointment with your doctor.

If you have taken several tests at home, but have gotten different results, a blood test will give you a definite answer and you will be able to discuss your concerns.

If the test is negative, but your period doesn’t start and you are experiencing symptoms of pregnancy, such as nausea, vomiting, tender breasts, or fatigue, your doctor can further examine you to determine the reason for what you are experiencing and tell you what steps should be taken to get your cycle back on the track.

If the test is positive, your doctor will be able to advise you about what to do next. If you wish the keep the pregnancy, your doctor can provide information about what to expect and get you started on supplements and a healthy regimen of diet and exercise that will give your baby the best possible start in life. If the pregnancy is unplanned and unwanted, or if there are medical contraindications, your doctor can advise you on safe methods to terminate gestation.

You can track your period using WomanLog. Download WomanLog now:

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https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940
https://www.aboutkidshealth.ca/fr/Article?contentid=345&language=French
https://www.who.int/fr/news-room/fact-sheets/detail/emergency-contraception
https://www.webmd.com/baby/guide/pregnancy-tests#1
https://www.webmd.com/baby/video/eddleman-trust-drugstore-pregnancy-test
https://www.passeportsante.net/fr/grossesse/Fiche.aspx?doc=test-grossesse-utilisation
https://blogs.webmd.com/womens-health/20070920/feel-pregnant-but-the-pregnancy-test-is-negative
https://www.webmd.com/baby/guide/pregnancy-tests#1
https://www.webmd.com/baby/qa/what-does-a-negative-pregnancy-test-result-mean
https://www.healthline.com/health/pregnancy/five-signs-to-take-pregnancy-test