hPL has been found to bind to the prolactin receptor with equal affinity to that of prolactin in rabbit milk fat gobule membrane, and hPL and prolactin have been found to possess very similar lactogenic activity in vitro in mouse and rat mammary gland explants .  In addition, hPL has been found to stimulate DNA synthesis in human mammary fibroadenoma cells transplanted into mice, which suggests that hPL promotes the growth of the human mammary gland similarly to prolactin.  As hPL circulates at concentrations that are 100-fold higher than those of prolactin during pregnancy, these findings suggest that hPL may play an important role in human mammogenesis during this time.  However, the relative affinities of hPL and prolactin for the human prolactin receptor have yet to be published and the effects of hPL on normal human mammary epithelial tissue have not yet been investigated, and so a definitive role of hPL in human mammary gland development during pregnancy has not been established at present. 
The blood level of hcG in a woman with an ectopic pregnancy usually rises at a slower rate than normal. Typically, hCG levels double about every two days for the first four weeks of a normal pregnancy, then slow to every 31/2 days by six weeks. Those with failing pregnancies will also frequently have a longer doubling time early on or may even show falling hCG concentrations during the doubling period. hCG concentrations will drop rapidly following a miscarriage. If hCG does not fall to undetectable levels, it may indicate remaining hCG-producing tissue that will need to be removed (dilation and curettage – D&C).