Pregnancy hormone is a common name for "human chorionic gonadotropin (hCG) The hormone is formed only during pregnancy and is almost exclusively formed in the placenta. It may play a role in nausea and vomiting often associated with pregnancy.
The milk hormone, scientifically named prolactin, is a hormone secreted by the pituitary gland, a tiny gland at the base of the brain. Prolactin levels are usually elevated in pregnant women and new mothers.