The test that allows us to know if pregnancy has been achieved is based on the analysis of the purported pregnancy hormone: beta-hCG. This test can be done both in urine and blood and qualitatively or quantitatively.
In this article we are going to explain the variations between the types, as well as the importance of knowing when the pregnancy test should be done after applying the assisted reproduction treatment.
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When should I take a pregnancy test?
Both in a natural pregnancy and in cases where assisted reproduction treatment such as in vitro fertilisation (IVF) is applied, it is recommended to wait at least 14 days from conception in order to carry out a pregnancy test and obtain a reliable result.
In a natural pregnancy, knowing the exact moment of fertilization is complicated and, therefore, the advice is to do the test after confirming the delay of menstruation. In the case of getting pregnant through a reproductive treatment, one should wait about two weeks after artificial insemination or the transfer of embryos in IVF.
If we test early, we can get a wrong result, either a false positive or a false negative.
False negative
As mentioned above, pregnancy tests measure the hormone beta-hCG. This hormone is released by the embryo from its implantation and increases its level progressively until the end of the first trimester, when it stabilizes.
If we do the pregnancy test early, the beta-hCG level may not have increased enough to be detected by the test. In other words, the beta-hCG value may be lower than the detection limit value of the test (test sensitivity).
In this way, even if there is gestational development, the test will be negative. Therefore, we will be faced with a false negative result.
False positive
We may also get a positive pregnancy test but later find out that there is no pregnancy or that this is not a normal pregnancy. We are therefore talking about false positives.
There are different situations that can give rise to this type of results:
- Ectopic pregnanc: occurs when the embryo implants outside the uterine cavity. This type of pregnancy is not evolutionary and in many cases it is necessary to intervene to eliminate the embryo.
- Anembrionic pregnancy: occurs when there is a gestational sac but no embryo growing inside it.
- Biochemical pregnancy: the embryo implants but stops its development within a few days. It's understood as a very early abortion.
- Remains of medication indicated for fertility treatment: in many IVF treatments, the patient is given hCG hormone to trigger ovulation. The traces of this hormone can be detected by the test.
- Ovarian tumor: One of the markers of this type of tumor is the increased level of beta-hCG.
It is important to note that false positives are much less common than false negatives. In addition, with the exception of fertility treatments, it is not in our power to avoid them.
How to do a pregnancy test?
There are currently two forms of pregnancy test: urine and blood tests.
Urine tests
The urine pregnancy test, known as early detection pregnancy test, can be purchased at any pharmacy and is able to detect beta hCG concentrations above 25-50 mUI/ml of hormone, depending on the specific sensitivity of the test we buy.
This is a qualitative analysis, i.e. the result is positive or negative. It is recommended to do the test with the first morning urine, which is the most concentrated.
Blood tests
They are generally more reliable than urine, as they have a lower sensitivity. In fact, they are able to detect pregnancy hormone concentrations starting at 10 mIU/ml.
There are two types:
- Qualitative: they are similar to urine, i.e. they only indicate a yes or no as a result.
- Quantitative: indicates the amount of beta-hCG hormone and based on this, the specialist indicates whether or not there is gestation.
Values below 10 mUI/ml are doubtful. In these cases, the test must be repeated about 2 or 3 days later in order to study the evolution of the hormone. If the value increases, approximately twice every 48 hours, we will be able to confirm the state of pregnancy. Conversely, if the value stagnates or even decreases, the result is negative.
Also, if the test is negative and the period still does not come, the test is repeated in 4-5 days in case it could be a false negative.
Although urine tests have a 95-97% reliability, it is advisable to perform the blood pregnancy test in a health clinic that has the necessary elements for hormone analysis.
Thus, the result is valued by the specialist and is therefore much more reliable. In any case, confirmation of gestation will only be obtained with fetal ultrasound, from 6th-7th weeks of pregnancy. In this ultrasound, it will be assessed if there is gestational sac and embryonic development.
Pregnancy test in Surrogacy
In surrogacy, the pregnancy test is performed on the surrogate mother or also called gestational carrier, since she is the woman to whose uterus the embryo has been transferred.
As in any other in vitro fertilization process, it is necessary to wait the necessary time to perform the test and obtain a reliable result. The anxiety of the intended partens can cause them to incite the surrogate mother to do the home pregnancy test before the indicated date. This practice is strongly discouraged, as it may create false expectations.
It is recommended that both surrogate mother and future parents have patience and follow the recommendations of the specialists who are carrying out the treatment.
In addition, it is essential that the surrogate mother goes to the clinic to find out if she is pregnant. In this way, not only is the result more reliable, but it can also receive the first medical indications in relation to gestational health and embryonic evolution.
FAQs from users
Do intended parents have to be present at the time of the pregnancy test?
They don't have to. It's optional. Some intended parents want to be present at this time and others don't give it more importance or it's not possible for them.
In some occasions, the gestational carrier may send the future parents the results of the analysis confirming the result, as well as the ultrasound. There are also cases in which, via Skype, the parents live the moment of knowing the news that their future child is on the way.
Is it easier to get a false negative in the urine test than in the blood test?
Yes, because of the higher sensitivity of home pregnancy tests, it is more common to get a false negative result. To avoid this, it is necessary to do the test correctly, i.e. with the first urine in the morning and on the indicated day.
Suggested for you
In addition to attending the ultrasounds marked by the specialist, it is important for the surrogate to have a rigorous medical check-up to avoid possible problems, both in her health and that of the baby. In cases of surrogacy, the intended parents worry about the surrogate mother and are interested in following the details of the day to day of the pregnancy. Do you want to know how the pregnancy is monitored? Find it out here: How the pregnancy evolves
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