When to take a pregnancy test to get a reliable result

Today there are many ways of finding out whether or not you are pregnant, and the pregnancy test is the most widely used of them all. There are countless pregnancy tests we can buy with just one click, but their result leaves us with doubts, especially about when to take a pregnancy test, or whether we have done it correctly. That is why our team of midwives at Happymami bring you the latest evidence on pregnancy tests, so that when you see your result, you know it is the right one.

When does a pregnancy test turn positive?

The quick answer, for the standard pharmacy pregnancy tests that measure human chorionic gonadotropin (HCG): if you are pregnant, it will turn positive 14-15 days after having unprotected sex, or 3 or 4 days after the date your period was due, provided your periods are regular, and I will explain why.

How does a pregnancy test work?

Nowadays, diagnosing pregnancy rarely poses any difficulties, thanks to the progress made in recent decades in complementary testing, which makes it possible to identify a pregnancy early with a sensitivity and specificity very close to 100 %, and an almost non-existent margin of error.

The pregnancy test is based on detecting HCG, a hormone synthesised during pregnancy. hCG is produced in the placenta by the syncytiotrophoblast, making it the main source of progesterone during the first 6 weeks of pregnancy, until the placenta takes over its production.

The synthesis of hCG begins on the day the fertilised egg implants, and its levels double every two days until they reach their peak at around 60-70 days of pregnancy. From then on, the hCG concentration falls to a plateau between 100 and 130 days, and remains there for the rest of the pregnancy.

When is the best time to take a pregnancy test?

hCG appears in maternal blood 8-9 days after ovulation, but it cannot be detected in urine until it reaches a level of 500 mIU/ml, which corresponds to 4 – 5 days of a missed period. That is the best time to take a pregnancy test.

My test line looks faint, what does that mean?

Bear in mind that for a pregnancy test to turn positive, 2 lines have to appear. The control line, which shows that the test has been done properly, and the line that detects the hCG hormone, which shows that you are pregnant.

So if both lines are marked, but one of them only faintly, this is probably because the amount of pregnancy hormone concentrated in your urine is not enough to get a “strong” positive, but it would still indicate that you are already pregnant. If you were to repeat the test in a few days, that line would probably be much more marked.

Which pregnancy test is the most reliable?

Nowadays, the number of pregnancy tests on the market is huge, and their reliability is high, since detection is not complex. Some brands even help you work out the weeks of pregnancy. (By assessing the hCG levels in your urine)

It is true that you will find different opinions about each pregnancy test, and bear in mind that not everyone knows when a pregnancy test should be taken, and depending on whether you take it sooner or later it can give false negatives.

That said, the most reliable tests are a blood test and an ultrasound scan, but that should not send you off to A&E to find out whether or not you are pregnant. If you follow the instructions that come with the pregnancy test you have decided to buy, it is very likely that the result will match reality.

How do I take a pregnancy test?

Bear in mind that once you have waited the right amount of time, 4 or 5 days after your period is late, if it is regular. Our recommendation is that you use your first urine of the morning to take the pregnancy test. This is because at that moment the urine concentration is higher and the hCG hormone is more condensed. The instructions for the pregnancy test you have bought may not tell you to do it this way, but our recommendation is undoubtedly to do so.

My pregnancy test is positive, what should I do now?

First of all, congratulations, and remember that in Spain a pregnancy follow-up is now set up with your midwife throughout your pregnancy and with gynaecology, until you give birth to your baby. So what you need to do is, after testing positive on your pregnancy test, get in touch with your midwife, who will give you an appointment and start the whole monitoring procedure. Pregnancy care begins with the booking visit or first appointment. This first antenatal appointment should take place during the first 12 weeks of pregnancy, ideally before the 10th week, which allows for early identification of the pregnant woman and proper planning of the actions to be carried out throughout the whole pregnancy

History of the pregnancy test

A little general knowledge, which in this case is also really interesting, is how pregnancy tests have evolved. If we go back to 1750 BC, a pregnancy diagnosis was carried out by moistening grains of wheat with the urine of the possibly pregnant woman; if they germinated, there was a pregnancy.

The Brugsch Papyrus, also known as the Berlin Papyrus (1350 BC), contained a diagnostic test that was widely used afterwards. It consisted of giving the woman the juice of a crushed watermelon mixed with the milk of a woman who had just given birth to drink; if the woman vomited, she was pregnant.

Another papyrus, the Carlsberg papyrus, showed another method based on leaving a piece of onion in the woman's vagina overnight, and if it kept its original taste the next day, the patient was pregnant.

Hippocrates of Cos used a technique that was very widespread in the following centuries. The women swallowed a syrup made from honey and water before going to sleep. If they were pregnant, this potion would give them colic; if they were not, it gave them a pleasant rest.

In 1927 the first biological pregnancy analysis appeared, developed by Zondek and Aschheim. After injecting the urine of a pregnant woman into an immature female mouse, changes similar to those that occur in the reproductive system of a pregnant woman were observed. This marked a new stage in the diagnosis of pregnancy.

Another diagnostic technique widely used until the early 70s was the frog test, proposed by Galli-Mainini in 1947. The reaction is based on the rapid ejaculatory response obtained in the animal by injecting the hormone chorionic gonadotropin (hCG), present in the urine of the pregnant woman.

Conclusion: when to take a pregnancy test

As we always tell you, every case is different and you will have to adapt this information to your particular situation. Be patient about the days on which you take the test, so that you do not spend money on pregnancy tests that come back negative when you know you took them too early, only to buy another one. And if the result is positive, CONGRATULATIONS! Welcome to motherhood, an intense… very intense stage, but a rewarding one at the same time. You know you can count on us for whatever you need.

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