Cerclage With Progesterone Versus Progesterone Only in Singleton Pregnancies

Inclusion Criteria: * Maternal age ≥18 years * Singleton pregnancy * Cervical length ≤ 25 mm, measured by TVS at the second-trimester ultrasonography (16 0/7 - 24 0/7 weeks of gestation) * Not participating in any other study which has intervention on maternity or fetus * Provision of written informed consent as shown by a signature on the participant consent form. Exclusion Criteria: * Cervical dilation with visible amniotic membranes or amniotic membranes prolapsed into the vagina * Major congenital abnormalities of the fetus * Intrauterine fetal demise * Presence of severe vaginal discharge\* * Presence of vaginitis or cervicitis\* * Presence of vaginal bleeding\* * Placenta previa or vasa previa * Preterm premature rupture of membranes * Preterm labor without ruptured membrane at the time of screening * Suspected chorioamnionitis * Unable to undergo cerclage * Cerclage in place * Allergy to progesterone (\*Women with acute cervicitis, vaginitis or severe vaginal discharge are eligible once they have been treated and if they have a CL ≤25 mm between 16 0/7 - 24 0/7 weeks of gestation.)