Action of the test for definition of early pregnancy is based on definition of a specific hormone of pregnancy - ganadotropin (HGCH) which starts to be developed in 1 day after implantation (attachment) of the impregnated egg to a uterus wall.
How there is a conception?
Maturing of an egg and its exit from an Home Pregnancy Test Dollar ovarie ovulation occurs approximately for 14 days prior to the beginning of a menstruation at a 28-day menstrual cycle.
Fertilisation of this egg probably approximately during 3 - 4 days. According to various authors, fertilisation terms can be from 12 - 24 hours till 7 days. The survival rate of spermatozoas in a female henital path depends in many respects on properties of a seed liquid. Mobility of Home Pregnancy Test Dollar spermatozoas remains longer, than their ability to fertilisation.
After eggs fertilisation moves ahead on a pipe in a uterus cavity. Germ transportation in a direction to a uterus proceeds during 5 - 6 days. Having reached the uterus cavity, the impregnated egg during some time is in a free condition and on 6 - 7 days of the pre-natal period are attached ("sticks") to an endometris then starts to take root actively in mucous a uterus (is implanted).
Since this moment pregnancy starts to develop, as is reflected by development of a hormone of pregnancy - ganadotropin. Thus, some days prior to an expected menstruation, in an organism there Home Pregnancy Test Dollar are traces HGCH which can be defined in urine house methods from 1st day of a delay of a menstruation.
In medical institutions spend definition HGCH in blood, revealing pregnancy some days prior to term of an expected menstruation, since sensitivity of a "blood" method much above.
The mechanism of work of the test for pregnancy
In tests for pregnancy it is used - the version of the analysis based on interaction of defined substance (usually albuminous nature) with antibodies to it. By the same principle of interaction the antigene-antibody works immune system of an organism, from here and the name.
As defined substance ganadotropin of the person (HGCH) - a hormone allocated with a placenta during pregnancy serves. Occurrence and fast growth of concentration HGCH in an organism (and in particular, in urine) women does by its authentic enough sign of pregnancy. Usually, for 7-10th day after fertilisation, concentration HGCH reaches 25 mme/ml (international units on ml) and doubles each 2-3 days, reaching a maximum between 8th and 11th weeks of pregnancy, and then decreases practically to zero to the beginning of 3rd trimester. 25 mme/ml are the minimum concentration HGCH detected by means of tests.
The test strip contains (fragile connection) antibodies to HGCH with dye. When the sample of urine moves on an absorbing strip, contacts HGCH and forms a complex an antigene-antibody. In a zone of positive reaction ("a pregnant strip") the complex contacts anti-hgch-antibodies. Dye is thus liberated and the red-pink strip is formed. If HGCH in the sample is absent, any strip, clearly, it is not formed. In the meantime urine moves further, passes a zone of positive reaction and reaches zones of Home Pregnancy Test Dollar negative reaction ("a control strip"). There untied the antibody-dye communicates reagents of a control strip, dye is liberated and the second (control) strip of the same red-pink colour is formed. All reactions occur during 3-5, 7 minutes are more rare
In not too qualitative tests dye can earlier, than all complex will reach an antibody-hgch-dye of reactionary zones, forming indistinct stains. They also are accepted more often to result. The present positive results meet much less often and are caused by quite concrete reasons. Also the weak second strip can be shown if to "overdo" the test, i.e. to read out indications not in 5 minutes specified on packing, and later. Such line results from evaporation of water from a test surface from what collapse dye is liberated. So it is not necessary to wait for 10 mines instead of 5 that "precisely to be convinced".
As precisely to carry out all instructions and correctly interpret results of the test each woman, doctors, especially an old school can not, are not inclined to trust tests.
What defines the test for pregnancy?
The test for pregnancy defines ganadotropin of the person (HGCH) - a hormone allocated with a placenta from the moment of implantation of an embryo in a wall of a uterus during all pregnancy. Reliability of this test rather high - is not present a placenta, is not present and HG. HGCH it is possible to define as in blood (in laboratory), and in urine (in laboratories and houses)
For what day after ovulation it is possible to carry out the test?
Basically, the positive result can be received for 7th day after ovulation. On embryo implantation 6-12 days, usually about 10 days are necessary. So it makes sense to wait for 10-12 days after ovulation, but even in this case often there are negative results (i.e., pregnancy is, but the test negative).
Tests of different manufacturers have various sensitivity, the majority of them are calculated on use from 1st day of a delay of the monthly. In 90 % yo 5 % of cases by this time the embryo is already implanted into a wall of a uterus and starts to develop HGCH. However in 10 % of cases of implantation has not occurred yet. At a delay in Home Pregnancy Test Dollar 1 week implantation occurs already in 97 % yo 3 % of cases. However in practice reliability of tests is limited by their sensitivity, so real reliability a little bit more low. As level HGCH doubles each 2-3 days, the recommendation from here follows: at negative result if the monthly do not begin to repeat the test in some days.
What mean results of the test?
The positive result is when the test shows two strips for lack of pregnancy. So happens, when the woman accepts the preparations containing HGCH, and also at tumours. After a spontaneous Miscarriage or abortion on early terms or removals of extra-uterine pregnancy HGCH during some time remains in an organism, and the test yields positive results (i.e. pregnancy already is not present, and the test still positive). As well as in case of reception of the preparations containing HGCH, for reception of authentic results it is necessary to make two quantitative definitions HGCH with an interval in 2-3 days. Reduction of level HGCH testifies that pregnancy already is not present. Thus, positive results - a relative rarity, unlike negative. The last turn out when pregnancy term is still too small also level HGCH is too low, that it was found out by the test (or the test in itself insufficiently sensitive).
Reliability of the house test depends on the various reasons:
Quality of the test. Production of different firms can differ considerably.
Working life of the test, condition and place of its storage. It is considered, that in most cases the test can be trusted provided that it is bought in a drugstore.
Pregnancy condition. At the pregnancy which is on the verge of a Miscarriage, HG it will be developed much less, than at normally developing pregnancy.
Conditions of statement of the test: research is necessary for spending, using a morning portion of urine in which the maximum maintenance of a hormone is observed; the test estimation is necessary for spending, adhering to a time interval specified in the instruction.
Additional circumstances. Home Pregnancy Test Dollar Maintenance HG in urine is influenced by a diet and a functional condition of your kidneys.
If overnight you have drunk a lot of liquid either have eaten a water-melon, or accept (diuretics), concentration of hormones in urine will be too low, and the test "will not notice" them.
If you in urine have a fiber (even if you know nothing about it) - the test can yield wrong result.
If to you entered HGCH for the purpose of an ovulation induction (preparations of pregnils) or for phase maintenance traces of this hormone can remain in your organism within 10 days after last reception of a preparation, and, accordingly, the test for pregnancy can yield positive result.
Also level HGCH can be defined in some weeks after normal sorts, sections, spontaneous or medical abortion and in other cases specified above.
As a result it is possible to receive the incorrect information, and in both parties: pregnancy is not present, but the test like the positive. Or: pregnancy is, but the test while the negative. Both that, and Home Pregnancy Test Dollar another happens a source of the big experiences.
