Pregnancy tests primarily detect which hormone in pregnant women?

Pregnancy tests primarily detect human chorionic gonadotropin (HCG), which is the hormone produced shortly after a fertilized egg attaches to the uterine lining. This hormone plays a crucial role in maintaining pregnancy by promoting the production of progesterone and preventing menstruation. HCG is typically detected in urine or blood tests, making it the standard hormone measured to confirm pregnancy.

In the early stages of pregnancy, HCG levels double approximately every 48 to 72 hours, which is why it is an effective marker for confirming pregnancy through tests. The presence of HCG in the system is what signals various physiological changes in the body, facilitating early pregnancy development and supporting the growth of the embryo.

Other hormones like progesterone and estrogen are involved in maintaining pregnancy and regulating reproductive functions, but they are not specifically indicative of pregnancy status in the same way HCG is. Human placental lactogen, produced by the placenta, also plays a role in metabolism during pregnancy but does not serve as a marker for early pregnancy confirmation. Thus, HCG is the definitive hormone targeted in pregnancy tests.