Women who subjectively suspect that they could become pregnant usually do tests to determine the "interesting position" earlier than others. And sometimes they don't see the expected two stripes either before the delay or after it. Whether the test can be wrong and not show pregnancy, if any, this article will tell.
Operating principle
Manufacturers of all pregnancy tests, without exception, use the same technology - test systems of any type (strip strips, tablet and inkjet, digital) determine in the urine an increased level of a special, unique hormone of pregnant women - chorionic gonadotropin. As soon as the level of this hormone in urine begins to exceed the sensitivity threshold of a certain test, the test area, on which the reagent sensitive to hCG is applied, is colored, this is the very second strip, which indicates a positive result.
Where does hCG come from, how it increases - we will consider in more detail. Chorionic gonadotropin is present in the blood in small amounts in men and women outside of pregnancy. Its content is usually so small that it is almost not given significant diagnostic value - from 0 to 5.0 mU / ml.
Tests cannot determine this number, and therefore, in non-pregnant women, a second strip is not displayed on the test system.
In the first days after fertilization (within 7-9 days), the embryo moves along the fallopian tube, descends into the uterus and gradually begins the implantation process. It first goes through the stage of adhesion (adhesion to the wall of the uterus), and then the villi of the outer layer of the ovum begin to produce a complex enzyme that dissolves the endometrial cells. This forms a depression into which the embryo sinks comfortably. The chorionic villi are connected to the mother's blood vessels.
From mother's blood already on the 7-9th day after ovulation, the unborn child begins to receive the substances and oxygen he needs. And the villi begin to produce hCG in high doses, while the concentration of the hormone in the blood grows quite quickly - every two days it doubles.
Why is this needed, you ask. On the ovary, after ovulation, at the place where there was a follicle with an egg, a temporary endocrine gland appears, which is called the corpus luteum. It produces progesterone, a hormone necessary for the proper functioning of the female body in the second phase of the menstrual cycle and in the early stages of pregnancy before the formation of the placenta.
If there is no pregnancy, the corpus luteum regresses and within 10-12 days after the formation stops the production of progesterone and resolves. The hormonal background changes, and menstruation begins. With the onset of pregnancy, progesterone softens and increases the thickness of the endometrium to facilitate the task of implantation, reduces the tone of the uterus, suppresses the aggressive immunity of a woman, which can mistakenly recognize the fetus as a foreign object and attack it, and prevents the onset of menstruation.
HCG grows until the end of the first trimester. Then the placenta takes over the endocrine functions, and hCG should no longer support the corpus luteum, which naturally regresses.
Thus, the principle of the tests is based on establishing the presence of a high level of hCG. Systems for home use, of course, cannot establish its exact quantitative content, for this there is a laboratory blood test for the content of chorionic gonadotropin.
But the very fact of an increase in the level of the hormone, the test can catch with high accuracy.
Optimal timing for testing
One of the most common reasons why the test may not show pregnancy in its actual presence is the failure to comply with the timing of the diagnosis. In other words, women begin to do tests too early when the concentration of human chorionic gonadotropin is still low.
We know that active production of hCG begins immediately after implantation of the embryo into the wall of the uterus, and then every 48 hours the hormone doubles. That is, the level of hCG in the blood for the first time oversteps the "non-pregnant" norms only 3-4 days after implantation, that is, 3-4 days before the date of the expected menstruation. But it is in the blood. AT In urine, the concentration of the substance is always lower, and it is for this reason that the test manufacturers recommend that the first test be done no earlier than the first day after the start of the delay.
Much also depends on the type of test device you choose. Strip strips are less accurate and digital tests are much less likely to fail. On the other hand, the stripes are able to catch the second stripe, faint, weak, when the hCG level is just beginning to rise, but digital devices cannot.
Different tests have different thresholds of sensitivity - the most sensitive are labeled on the packaging, stating that their threshold is from 10 to 15 mU / ml. Such tests begin to determine pregnancy earlier, even with a fuzzy second strip - already 3 days before the expected date of menstruation, under favorable circumstances, ultrasensitive test systems can indicate pregnancy, but you should not count on this.
Most of the popular tests, the most widespread among the fair sex, have a sensitivity threshold of 20 to 30 mU / ml. Such tests before the delay in menstruation are unlikely to become positive, but already on the first day of the delay, in most cases they are able to give a fairly accurate answer - positive or negative.
Therefore, the first day of the delay should be considered the best day to start self-diagnosis.
If there is no period as expected, and the test shows a very pale and weak second strip or does not show a second strip, do not despair. This does not always indicate the absence of pregnancy.
Reasons for a negative test after a delay
A negative or weakly positive test result, provided that there is a delay in menstruation, needs to be rechecked. The very fact of the absence of menstruation is an indirect sign of a possible pregnancy, although menstruation may not start for other reasons., for example, due to hormonal disruption, ovarian dysfunction, inflammation. In this case, the test will certainly remain negative on the second, and on the 4th day of the delay, and after 10 days. If there are no menses, then after 2 weeks of delay it is worth contacting a gynecologist to undergo an examination of the state of reproductive health.
Do not forget to observe your well-being, but do not exaggerate your feelings, do not look for them where they do not exist. And if, with the onset of the delay, you feel certain signs of a possible pregnancy (nausea in the morning, the chest is swollen and aches, the perception of tastes and smells has changed), and the test remains negative, you should consider the possible causes of this phenomenon.
Late ovulation and implantation
Not all women track their ovulation by ultrasound or do ovulation tests. Therefore, most women cannot know for sure at least an approximate day (plus or minus a day or two) when the egg was released and the subsequent conception of the baby. But in the minds of the people, the idea that ladies get from the Internet, that ovulation always falls in the middle of the cycle, has firmly settled down.
It's a delusion. There is early ovulation, which occurs before the 12th day of the cycle, and there is late, which can occur just a week before the expected menstruation. Various factors can affect this delicate and delicate process - from stress, workload and chronic fatigue to hormonal disorders, hypothalamic-pituitary anomalies, and inflammatory processes in the body. A cold, flu, business trip or vacation, especially if they were associated with a change in the time and climatic zone, flight, can affect ovulatory processes and shift an important day of the female cycle to a later or earlier time.
We will not talk about early ovulation. With her, the egg is usually immature, and the very fact of conception is unlikely, but if this happens, then in these cases "striped" tests become a record 6-7 days before menstruation (there are many such examples with photographs on the Internet). We are interested in late ovulation. It is more common, and it is she who shifts the implantation by 7-9 days.
Therefore, it is not surprising that at the beginning of the delay, the test for the onset of pregnancy remains negative.
If ovulation is only 4 days late, then ovulation also occurs later, and by the expected day of delay, the amount of hCG has not yet had time to accumulate in an amount sufficient for the test to catch.
With timely ovulation, late implantation occurs. The mechanisms of this process have not yet been sufficiently studied by physicians, and it is difficult to say why some embryos begin the adhesion stage as early as 5 days after fertilization, while others float freely in the uterus, where they have reached through the fallopian tube, for several days, and only 9 10th day of the cycle. After 10 days, implantation is unlikely, even if conception was - physiological changes in the endometrium during the extinction of the corpus luteum will not allow the process of introducing the ovum into the endometrium to occur.
Let's try to calculate when the test, when ovulation is 4-5 days late, can show a positive result: if ovulation did not occur on day 14 of the cycle with its 28-day duration, but only on day 18 or 19, then implantation will occur on average 23 -25 day of the cycle, and the first results of the tests will show only 6-8 days after implantation, that is, a week after the start of the delay.
Ectopic pregnancy
With such a pathology, the fixation of the ovum does not occur in the uterus, but outside it, in 97% of cases - in the fallopian tube. In this case, the chorion also produces hCG, but its content is much lower and the growth (dynamics) is slower. That is why in case of an ectopic pregnancy, the test may not show anything until the delay, and after it begins, it may give either a negative or a weakly positive result (the second strip is doubtful, very pale).
Freezing early pregnancy
The term 3-4 weeks of pregnancy from the date of the last menstruation, that is, according to the obstetric standard, is considered one of the most dangerous in terms of the likelihood of stopping the development of the embryo. In this case, a frozen pregnancy occurs. From the moment the embryo dies, hCG ceases to be produced, or for another 2-3 days, the production remains in insignificant concentrations. The hCG level does not stay in one place for a long time, and then begins to decline.
In this case, the test may not show the second strip, in general, neither before nor after the delay, if the embryo died before the concentration of the hormone reached the sensitivity threshold of the test systems.
If the hormone has been developed enough before the death of the baby, then the tests show a weak second strip, which does not become brighter when re-diagnosed either 2 or 4 days after the first test.
Self-diagnosis errors
Finally, a test error could be the cause. Read the instructions carefully. Do not keep the test longer than the specified time in urine, do not immerse it in liquid deeper than the control line, do not wait for the result for hours. If everything is done according to the instructions, the probability of error will be minimal.
You need to check the expiration date of the test and the integrity of its packaging - expired tests are almost always wrong. Test on the morning urine sample (it is the most concentrated). Before the test for 4-5 hours do not drink liquids, do not eat foods with a high liquid content.
What to do?
If a delay begins and the test remains negative, be patient and wait about a week more. During this week, carefully monitor your health - if there are pains in the abdomen, lower back, bloody spotting, the temperature rises, you should immediately consult a doctor.
Retests should not be done every day. Knowing that hCG builds up every 48 hours, it is wiser to repeat the self-test every other day. A week later (in the alleged fifth obstetric week), using ultrasound, doctors can already detect a fertilized egg, if any, establish whether a woman has a uterine or ectopic pregnancy, whether there are signs of inflammation, neoplasms.
If there is no strength to wait (which is quite understandable), go to any clinic and have a blood test for hCG. Its amount at the level of 0-5 mU / ml clearly indicates the absence of pregnancy. Underestimated indicators above this level can speak of both frozen and ectopic pregnancy. It is important to retake blood and see the dynamics of hCG after 48 hours.
