Progesterone in Women with Recurrent Miscarriages

To the Editor: In summarizing their well-executed randomized trial, Progesterone in Recurrent Miscarriages (PROMISE), Coomarasamy et al. (Nov. 26 issue) 1 state that there is no evidence of benefit from progesterone supplementation “in the first trimester” of pregnancy among women who have had three or more miscarriages. We wish to clarify three points. First, the trial did not address progesterone supplementation in women with coexisting subfertility. Nearly 33% of the women screened for the trial were excluded because of subfertility (515 of 1568 women). Second, because progesterone plays a key role in the implantation of the embryo, benefit from supplementation may . . .