VF Test for Prediction of Extremely PTB After Cerclage

The purpose of this research study is to determine if a vaginal fluid (VF) test can predict very early preterm birth in patients who are scheduled to have an exam indicated cerclage for severe cervical shortening. Prior to participants undergoing a scheduled amniocentesis two swabs to collect vaginal secretions for the VF tests will be done. During the amniocentesis your doctor will remove amniotic fluid as part of the routine clinical care. From that fluid sample, the study will use less than a quarter teaspoon for the amniotic fluid study test (AF test). Data regarding maternal and birth outcomes will be collected by medical record review.