Major fetal abnormalities (defined as those that are lethal or require prenatal or postnatal surgery), fetal death, or fetal growth restriction diagnosed before randomization.

Presence of prophylactic cervical cerclage

Significant maternal-fetal complications (treated chronic hypertension, insulin dependant diabetes mellitus, red cell isoimmunization)

Painful regular uterine contractions, or ruptured membranes

Visual cervical dilation of 2cm or greater and visible membranes.

Patients with a pregnancy dated by an ultrasound after 20 weeks gestation.

Preventing Preterm Birth With a Pessary

What this study is about