Oral but not transdermal estrogen is associated with an increased blood clot (DVT) risk. In addition, our data suggest that norpregnane derivatives may be thrombogenic, whereas micronized progesterone and pregnane derivatives appear safe with respect to thrombotic risk. If confirmed, these findings could benefit women in the management of their menopausal symptoms with respect to the blood clot (DVT) risk associated with oral estrogen and use of progestogens.