Feasibility Study and Predictive Value of the Uterine Cervix Polarimetric Imaging for the Management of the Threat of Premature Delivery : The POLARMAP Project

Prematurity is the first cause of perinatal mortality and morbidity worldwide. The threat of premature delivery (TPD), the most important complication and the leading cause of hospitalization during pregnancy has multiple origins which are seldom precisely identified.

In Belgium and Europe, the estimated rate of premature births is about 10 %. This rate has been stable over the last two decades in spite of the introduction of new tocolytic treatments and the use of cervical length measurement by transvaginal ultrasound to assess the risk of preterm birth.

The standard medical examination for the detection of patients with TPD is the endovaginal ultrasonographic examination of uterine cervix (echography). Ultrasound examination is more accurate and reproducible compared to cervical digital one, and it possesses two essential qualities of a diagnostic examination: it is easily accepted by the patients and the learning curve is fast.

This technique is validated with well-known criteria, namely, the shortening of the effective length and the opening of the internal orifice of the cervix. The threshold for these two criteria depends on the practitioner's choice: at 30 mm effective length, the sensitivity and negative predictive values are high, but the specificity is poor, while the opposite is true if the threshold is set at 20 mm.

Ultrasound examination for the identification of the patients at risk of premature delivery is a real improvement over cervical digital examination. However, this technique is not ideal, due to the lack of objective criteria for the choice of threshold, because of the imperfect correlation ("noise") between the measured effective length of uterine cervix and the time left before the birth. Moreover, the use of cervical ultrasonography in the strategy of premature delivery screening is not well established.Finally, the transvaginal ultrasound probes are not available in all perinatal centers that would be yet all concerned in case of preterm delivery.