A Randomized Trial of Pessary in Singleton Pregnancies With a Short Cervix

Inclusion Criteria: * Singleton gestation. Twin gestation reduced to singleton either spontaneously or therapeutically, is not eligible unless the reduction occurred before 13 weeks 6 days project gestational age. Higher order multifetal gestations reduced to singletons are not eligible. * Gestational age at randomization between 16 weeks 0 days and 23 weeks 6 days based on clinical information and evaluation of the earliest ultrasound. * Cervical length on transvaginal examination of less than or equal to 20 mm by a study certified sonographer. There is no lower cervical length threshold. Exclusion Criteria: * Cervical dilation (internal os) 3 cm or greater on digital examination or evidence of prolapsed membranes beyond the external cervical os either at the time of the qualifying cervical ultrasound examination or at a cervical exam immediately before randomization. * Fetal anomaly or imminent fetal demise. This includes lethal anomalies, or anomalies that may lead to early delivery or increased risk of neonatal death e.g., gastroschisis, spina bifida, serious karyotypic abnormalities. An ultrasound examination from 14 weeks 0 days to 23 weeks 6 days by project Estimated Date of Confinement (EDC) must be performed prior to randomization to evaluate the fetus for anomalies. * Previous spontaneous preterm birth between 16 weeks 0 days and 36 weeks 6 days. This includes induction for pPROM in a prior pregnancy. * Planned treatment with intramuscular 17-α hydroxy-progestero…