Study population
Study participants were identified using obstetrical delivery ICD10 encounter codes and sonogram CPT codes. Patients were included in the study if meeting the following screening TVUS and delivery criteria: age between 18 to 50 years, underwent TVUS CL screening at NYULH Maternal Fetal Care Center (MFCC) between 18 weeks 0 days – 23 weeks 6 days gestation during a routine anatomic survey, and delivered a live neonate at NYULH Tisch Hospital in the year 2018. Screened patients with multiple gestation pregnancy, medically indicated preterm birth, uterine anomalies, or cervical cerclage in situ were excluded. Enrolled patients were also excluded if TVUS cervical images were not electronically available from the medical record to review or if available images were suboptimal for assessment of the cervix. Demographics, clinical characteristics, and obstetrical outcomes were manually collected for all patients; short interpregnancy interval was defined as <18 months. As several of the predetermined exclusion criteria are known risk factors for PTB, we anticipated a relatively low-risk final study population; to determine the overall PTB rate at our institution, a post-hoc evaluation of all excluded patients was performed for gestational age (GA) at delivery to identify the number of PTBs inadvertently excluded from final analysis of the study cohort.