Image acquisition and review
TVUS cervical images were obtained using standardized CL Education and
Review (CLER) criteria by accredited sonographers with supervision by
maternal fetal medicine physicians at the NYU MFCC. Ultrasound units
with 4- to 9-MHz IC5-9D (Voluson e8; GE Healthcare, Milwaukee, WI) or 4-
to 8-MHz C8-4v (IU22; Phillips Healthcare, Andover, MD) wide-view
transducers were used to obtain all images 20. Stored
CL images were evaluated for this study by a single reviewer, who was
blinded to delivery outcome. Of the patients included in final analysis,
25% were randomly selected for a second review of stored CL images by
another study team member to confirm reliability of interpretation and
to calculate scores of interobserver variability. Cervical images were
assessed for quality, reported CL, and visibility of the CGA. Optimal
cervical imaging was defined as a sagittal view of the cervix with
clearly visible internal and external ostia, approximately equal
thickness anterior and posterior cervical lips, complete (or near
complete) visualization of the cervical canal, and minimal urine in the
maternal bladder 21.