Today I will explain one of those curiosities of science that many people do not know and whose knowledge has no impact: If a pregnant woman had a pregnancy test in the second or third trimester, it would probably be negative.
You may wonder how it can be. The reason for this is that the pregnancy test is not an indicator of the presence or not of a fetus, but a measure of the Chorionic Gonadotropin hormone, better known as hCG.
The moment a woman becomes pregnant, the hormone begins to segregate in large numbers with various functions. On the one hand it prevents the disintegration of the corpus luteum in the ovary (when a woman ovulates and pregnancy does not occur, the corpus luteum involves, lowers the hormonal production and menstruation appears), since it has the function of secreting very important hormones (I continue talking about the corpus luteum) during the first months of pregnancy. On the other hand, hCG intervenes in immune tolerance during pregnancy, although its main function is as previously mentioned.
The hCG is secreted from the sixth day of pregnancy until, at 2-3 months of gestation, the placenta begins to secrete hormones by itself. At that time the hCG secretion begins to descend until practically disappear.
As this hormone is the one that serves as a marker when it comes to positivizing a pregnancy, at the moment the pregnancy tests go down they could be negative. Obviously that does not mean that the woman is not pregnant (her belly, ultrasound and symptoms show that she is), but that the test is negative for hCG, neither more nor less.
In other words, when a woman takes a pregnancy test, the result is "positive for hCG" or rather, it means that hCG levels are high, however, there are other reasons (tumors, immunological reactions, etc.) that also produce an increase in this hormone and would be positive in the so-called pregnancy tests.
The conclusion drawn from this information is that Pregnancy tests should stop calling themselves that, their name should be "hCG test", to be more correct with their function.
