The role of human placental lactogen is:

HUMAN PLACENTAL LACTOGEN (hPL): This is also known as human chorionic somatomammotropin (hCS). It is synthesized by the syncytiotrophoblast of the placenta. The hormone is chemically and immunologically similar to pituitary growth hormone and prolactin. hPL in maternal serum is first detected during the 3rd week. The level rises progressively from 5 to 25 mg/mL until about 36 weeks. Functions: hPL antagonises insulin action. hPL causes maternal lipolysis and promotes transfer of glucose and amino acids to the fetus. As a potent angiogenic hormone, it helps to develop fetal vasculature. It promotes growth of breasts for lactation. Reference: Dutta's Textbook of Obstetrics 7th edition page no 60