As we said earlier, even though that is what one usually tends to believe, it does not mean that it is what actually happened. A missing period may be an indicator of several causes other than pregnancy. For this reason, women are always advised to visit an expert in order to obtain a medical diagnosis, this way allowing the woman to take matters into her own hands.
Many women go for a fast-track approach. To this end, several at-home, easy-to-use tests can be found, which advantage is that they have no difficulties whatsoever. They are commonly called home pregnancy tests (HPT) and work by detecting an hormone in the woman’s urine called human chorionic gonadotropin, also known as beta hCG.
The hCG hormone is only detectable when the woman is pregnant, that is to say, if the embryo has been able to attach to the endometrium. From that moment on, the woman begins producing beta hCG, which at the same time has an influence on progesterone production, a necessary stage for placenta development and embryo development after implantation.
This hormone can be detected either through blood or urine, obtaining in both cases highly accurate outcomes.
Pregnancy tests can show a negative result despite being pregnant if taken too early, that is, before your body begins secreting hCG hormone. This may occur in both blood and urine pregnancy test, although it is true that the former is usually more accurate than the latter. Pregnancy tests should be done in the following cases:
- Natural pregnancy: Pregnancy tests can be done whenever your period is late for at least one day (women which period is usually regular). If you have irregular menstrual periods, you are advised to take the pregnancy test within 18 days before you last engaged into sexual intercourse.
- Fertility treatments: You should take care for the two-week wait (2WW), or the period of time indicated by your physician. In general, it takes around 16-18 days after artificial insemination (AI) and 14-15 days post embryo transfer.
When detected in blood, the hCG hormone shows more accurate results, that is, getting false positive or false negative results are unlikely, something that may occur with a urine pregnancy test.
hCG levels should be evaluated by an expert, since them being too elevated or too low may help your gynecologist establish a schedule of prenatal care for you.
With urine pregnancy tests, if taken too early, it may happen that hCG levels are not enough for it to be detectable and show a positive result, in which case you would obtain a negative result when you are actually pregnant. This is commonly known as false negative. For this reason, following the directions established for this kind of tests is advisable. In this sense, HPT should be done using your first morning urine, since that is when the concentration of hCG reaches its highest peak as it is not too diluted.
Conversely, obtaining a false positive result is highly unlikely. This is due to the fact that, as stated before, hCG is only produced during pregnancy. This is more commonly related to the use of poor-quality pregnancy tests, which sensitivity is too low. It may also be due to a miscarriage that has occurred in the time interval between the test due date and your visit to the gynecologist.
This phenomenon is known as biochemical pregnancy and, if it were to happen, you are advised to visit your physician to determine whether hCG levels are too low. By doing this, you can avoid deceiving yourself because you got a positive result and later found out that no pregnancy really exists.
Beta hCG levels
hCG levels may vary greatly from woman to woman or even between pregnancies. There are cases in which hCG levels remain too low and that is when doubts may arise.
In such cases, attention should be paid not only to the particular hCG value obtained, but rather to the increase such levels may experience. As a general principle, beta hCG levels double every two days approximately.
Reference values may vary depending on the provider. For this reason, while there exist tests able to show a positive result from 5 mIU/ml, others do so from 25 mIU/ml, and another group from 50 mIU/ml upwards.
below you will find the general hCG reference values in blood, which can help you estimate how many weeks pregnant you are. For the establishment of each interval, the minimum value along with the maximum one that can be obtained during each week of pregnancy have been gathered—that is the reason why so much variability can be seen.
- 1-2 weeks pregnant: 5-120 mIU/ml.
- 2-4 weeks pregnant: 13-1.175 mIU/ml.
- 4-6 weeks pregnant: 45-80.500 mIU/ml.
- 6-16 weeks pregnant: 2.600-175.304 mIU/ml.
- >16 weeks pregnant: 21.160-65.730 mIU/ml.
Having pregnancy symptoms are not accurate indicators that pregnancy has occurred, as they can be easily mistaken for the premenstrual syndrome (PMS). Whenever you think you may be pregnant, you are advised to visit your doctor in order to get directions on how to proceed.