A Randomized Trial of Cerclage Versus 17 α-Hydroxyprogesterone Caproate for Treatment of a Short Cervix

Inclusion Criteria: * Ultrasonographic evidence of premature dilatation of the internal os * Prolapse of the chorio-amniotic membranes into the endocervical canal * Functional cervical length less than 25mm * Exacerbation of these ultrasound findings with transfundal and/or suprapubic pressure Exclusion Criteria: * Any fetal chromosomal or structural anomaly * Multiple gestation * Known allergy to progesterone * Ruptured membranes * Vaginal bleeding * Intra-amniotic infection (diagnosed clinically or by amniocentesis) * Prolapse of endocervical membranes beyond the external cervical os * Persistent uterine activity accompanied by cervical change * Obstetrically indicated delivery.