Predicting spontaneous PTB risk is improved when quantitative ultrasound data are included with clinical data

Abstract

Predicting women at risk for spontaneous preterm birth (sPTB) has been medically challenging due to the lack of signs and symptoms of preterm labor until intervention is too late. Hypothesis: Predicting the sPTB risk level is enhanced when using both historical clinical (HC) data and quantitative ultrasound (QUS) data compared to using only HC data, with HC data being defined as birth history prior current pregnancy as well as, from the current pregnancy, a clinical cervical length assessment, and data from a physical exam. Study population included 250 full-term births (FTBs) and 25 sPTBs. QUS scans (Siemens S2000 & MC9-4) were performed using a standard cervical length approach by RDMS sonographers. QUS is a measure of cervical remodeling at the microstructure level. Two cervical QUS scans were conducted at 20±2 and 24±2 weeks’ gestation. Multiple QUS features were evaluated from calibrated raw radiofrequency backscattered ultrasonic signals. Two statistical models designed to determine sPTB risk were compared: 1) HC data alone and 2) combined HC and QUS data. Test ROC AUC compared both models. The study’s birth outcomes were only FTBs or sPTBs; medically induced preterm births were not included. Combined HC and QUS data identified women at sPTB risk with better AUC (0.68; 95% CI, 0.58-0.78) than that of HC data alone (0.52; 95% CI, 0.38-0.65). A likelihood ratio test for significance of QUS features in the classification model was highly statistically significant (p < 0.01). Traditional risk factors for sPTB (age, parity, previous history of PTB, cervical length < 25 mm, smoking, BMI and alcohol use) were not predictive of sPTB in our sample of participants. Cervical length measurements and HC have been the mainstay of risk assessment for sPTB for years because no other credible biomarkers were available. Even with only 25 sPTBs, there was value-added for predicting sPTB when QUS data were included with HC data.