The corpus luteum is a temporary gland of internal secretion in a woman. It remains active for 10 to 12 weeks of pregnancy, producing progesterone necessary for the development and preservation of the fetus. Progesterone stimulates the growth of the uterine mucosa, inhibits the release of new eggs and prevents menstruation.
From the first days of pregnancy, the placenta, which forms after the conception of the fetus, secretes a specific hormone – human chorionic gonadotropin (hCG). It affects the development of the corpus luteum of the ovary.
How the test works
The level of chorionic hormone is growing rapidly and very soon it can be found in urine. A pregnancy test contains antibodies that interact with this hormone. When urine is dripped into a cassette, a capillary action causes the test urine to move across the membrane.
As a control method, in order to ensure that the test is carried out correctly, the first colored line should appear in the control zone area. If the woman is pregnant, then reaching the test region of the membrane, which interacts with hCG, a second color line appears.
Test Application Method
Collect urine in a clean, dry dish and dip the test strip into it to the level indicated by the arrows. After 5 to 10 seconds, remove the urine test and place it on a flat, dry surface.
During the first minute, a color wave should appear on the diagnostic field, which will slowly move. If it is not, it means that insufficient urine has got on an absorbent surface or it has not got at all.
You can get an answer after 1 – 5 minutes, but no later than 10 minutes.
How many days and when will the test show pregnancy after conception
An exciting question for a woman is when, after how many days you can use the test to know exactly whether conception occurred or not.
Human chorionic gonadotropin is present in the body in non-pregnant women and in men. In women, the hormone:
- stimulates egg growth in the ovary;
- provides completion of egg maturation in the follicle;
- creates the conditions for subsequent ovulation – rupture of the follicle and the release of the egg.
In men, the hormone regulates reproductive function, affects the maturation of sperm in men.
The normal level of hCG in healthy adults is 0-15 mIU / ml.
HCG levels have been rising since conception. The hormone begins to be produced at the stage of early embryonic development of the embryo, even before the fertilized egg attaches to the uterine wall. But the active production of the hormone is recorded immediately after implantation of the embryo. This is observed on the 6-8th day after the fertilization of the egg and lasts throughout the pregnancy.
Normally, hCG is found in the blood serum and urine of pregnant women 6 to 10 days after fertilization. Its content increases until the end of the first trimester of pregnancy, and then falls.
Table 1 will guide women through how many days they can diagnose. The table shows the findings of an early pregnancy clinical trial using the Clearblue digital test.
|The number of days before the expected menstruation||The number of women who received a positive response if they were pregnant|
|4 days before the expected cycle||55%|
|in 3 days||86%|
|in 2 days||97%|
|in 1 day||98%|
If the diagnosis is carried out before the first day of the expected cycle and the answer is “not pregnant”, then it is highly likely that the level of the hormone has not yet reached the amount necessary to determine pregnancy. Repeat the test on the first day of the cycle.
The accuracy of the Clearblue test is 99% if a woman uses it on the first day of the expected menstruation. The answer is consistent with the results of an ultrasound scan. The gestational age by weeks is 97% the same as the result of a later ultrasound. In comparing the results of 187 women (1 – 2, 2 – 3, 3 or more weeks after conception) and ultrasound results, the error was +/- 5 days.
Is it possible to do a test one week after unprotected intercourse?
The main marker of pregnancy is free β-hCG. The tissue of the outer layer of cells in a developing embryo begins to produce the β-subunit of the chorionic hormone a day after conception. During this period, the concentration of the hormone in the blood does not exceed 5 mIU / ml. And in the urine begins to be determined after two days.
With a normal pregnancy, the content of hCG doubles every 2 to 3 days. A week after unprotected intercourse, the concentration of the hormone in the urine will be low. The presence or absence of pregnancy during this period cannot be determined.
On which day of pregnancy the test will show a positive answer, depends on the physiological characteristics of each woman. Free β-hCG enters the bloodstream of the mother due to the secretion by the cells of the external cell mass of the embryo (trophoblast), as well as one of the decay products of hCG. Therefore, the appearance of free β-hCG in blood and urine may depend, for example, on the number or activity of placental macrophages – connective tissue cells that absorb destroyed cells and foreign organisms.
By the expected first day of the cycle, the hormone concentration varies in the range of 50-100 mIU / ml. Therefore, on the first day of the proposed onset of menstruation, the test may not show whether conception occurred or not. In some cases, pregnancy can be determined only five days after the delay in starting a new menstrual period.
The belief that the test shows two colored stripes a day after intercourse is wrong. To know the result is real only as the concentration of the hormone in urine increases. Highly sensitive tests give an answer 2 weeks (14 days) after the onset of ovulation. And in time, this usually coincides with the delay of the next menstruation. It is too early to diagnose one week after the expected moment of conception.
It is important to remember that a test can give a false positive or false negative answer.
Of the tests for independent use, the most are digital.
They have several advantages:
- the accuracy exceeds 99% if it is used on the first day of the expected start of a new menstrual cycle (on the day when menstruation should begin);
- have a high degree of sensitivity, so for most women in case of pregnancy they will show two strips even four days before the expected start of menstruation;
- the reagent interacts with hCG at its lowest concentrations (from 25 mIU / ml) in the urine;
- equipped with built-in control functions, which eliminates the possibility of error due to improper use.
In any case, all your doubts or incomprehensible results should be discussed with your doctor.