You Asked:

What hormone is in woman’s urine that indicates she’s pregnant? — Annie, Manchester, United Kingdom

Marshall Brain Answers:

The hormone is called human chorionic gonadotropin, or HCG. It is produced after the fertilized egg implants in the lining of the uterus. The following video shows the menstrual cycle and where HCG production begins in the cycle.

HCG production starts several days after implantation, so it is a good early indicator of pregnancy. HGC is normally present before the first period is missed. By the time the first period is missed and most women have a hint that fertilization may have occurred, HCG levels have ramped up and are easily detectable. You can find an in-depth discussion of pregnancy tests on this page.

More info on the reactions that occur in pregnancy tests:

See also: How Female Puberty Works