It is partly responsible for the frequent urination often experienced by pregnant women during the first trimester. Human chorionic gonadotrophin can be detected in the urine as early as 7-9 days after fertilisation and is used as an indicator of pregnancy in most over-the-counter pregnancy tests. This hormone enters the maternal circulation and allows the mother to recognisethe embryo and begin to change her body to support a pregnancy. When an egg is fertilised, it travels though the female reproductive tract and on day six implants into the womb releasing a hormone called human chorionic gonadotrophin in the process. The early stages of pregnancyįollowing conception, a new embryo must signal its presence to the mother, allowing her body to identify the start of pregnancy. Initially, the ovaries, and then later, the placenta, are the main producers of pregnancy-related hormones that are essential in creating and maintaining the correct conditions required for a successful pregnancy. In response to this, the target tissue or organ changes its function so that pregnancy is maintained. Hormones act as the body’s chemical messengers sending information and feeding back responses between different tissues and organs. Hormones travel around the body, usually via the blood, and attach to proteins on the cells called receptors – much like a key fits a lock or a hand fits a glove. The correct balance of hormones is essential for a successful pregnancy.