Palagiano 2004.

Methods	2‐arm placebo‐controlled randomised trial.
Participants	50 women were randomised in a hospital setting in Italy. The population comprised women with threatened abortion, an ongoing, viable pregnancy, amenorrhoea between 6 and 12 weeks' gestation, and a closed uterine cervix. Exclusion criteria comprised women with a previous adequate luteal phase, women who were using hormonal treatment or other drugs affecting uterine contractility, women with vaginal infection, absence of embryo’s heartbeat, open cervix (> 2 cm measured by ultrasound), and embryo’s size 1 week more than the corresponding amenorrhoea.
Interventions	90 mg micronized vaginal progesterone once daily for 5 days versus placebo.
Outcomes	The study recorded the following outcomes relevant for this review: miscarriage.
Notes	Evidence of trial documentation and data requested from the corresponding author, but no response was received by the time of publication of this review.