Progesterone for Threatened Abortion

Threatened abortion is defined as bleeding through the vagina, with a closed cervix, that occurs before the gestational age at which a fetus would be viable ex utero. Beyond this simple definition, some investigators have used additional criteria, such as confirmation that the source of the bleeding is from within the uterus and not from the cervix or vagina or requiring that the bleeding be more than mere "spotting." It is not surprising, then, that estimates of the incidence of threatened abortion vary considerably, with an incidence of approximately 25% being a reasonable contemporary estimate.1 For similar reasons, the estimate . . .