Patterns of cervical length and cervical consistency index in singleton gestations and the risk of preterm birth

Despite multiple efforts, the rate of spontaneous preterm birth continues to rise. However, despite the extensive use of cervical length in the last 30 years as screening to detect patients at risk of preterm birth, the percentage of preterm births has not decreased significantly, therefore a new approach is necessary to identify the risk of delivery. The cervical consistency index (CCI) was proposed as a sonographic marker, designed to assess cervical softness as a predictor of PTB. The purpose of this study was to compare the current binary view of the assessment of the cervical length (< 25 vs. >25 mm) versus the assessment based on the CCI. Prospective cohort study including singleton gestations between 11+0 and 34+6 weeks. The ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest was calculated off-line to obtain the CCI. sPTB was defined as a birth <37 +0 weeks related to the spontaneous onset of labour with intact membranes or with PPROMs. The relationship between CCI and CL and risk of PTB was analysed using logistic regression and the estimated probability of PTB by CCI and CL was calculated. A total of 1031 patients were included and prospectively followed. Cervical length was combined with CCI and patients were classified in four groups based on the risk to preterm birth. The groups were grouped as follow: 1. Group A: short cervix (<25mm) with normal consistency (ICC >10%) low risk (OR 1.4); 2. Group B: long cervix (> 25mm) with normal consistency (ICC >10%) very low risk (OR 1); 3. Group C: short cervix (<25mm) with low consistency (ICC <10%) very high risk (OR 6.1); 4. Group D: long cervix (>25mm) with low consistency (ICC < 10%) high risk (OR 4.8). The paradigm shift in the assessment of the cervix may help us to obtain a more accurate assessment of the risk of preterm birth and the natural history of the disease in each patient, and in line with personalised medicine of the 21st century.