The effect of cerclage and progesterone in high-risk singleton pregnancies has not been directly
compared in a randomized trial, but, in an indirect meta-analysis, the results of the above-mentioned
meta-analysis were compared with four randomised studies evaluating the effect of progesterone with
placebo [60]. Vaginal progesterone and cerclage were equally efficacious in the prevention of preterm
delivery in women with singleton gestations, previous preterm delivery and a short cervix in the
second trimester