[Prediction of preterm delivery in symptomatic women (preterm labor)]

To evaluate the predictors of spontaneous preterm birth in case of preterm labor.

Literature search in Medline and Cochrane databases and recommendations of international societies. Selection of studies in symptomatic women (with preterm labor).

Preterm labor is defined as a clinical situation occurring between 22 and 36 weeks + 6 days, in which cervical changes are observed associated with uterine contractions, evolving spontaneously or not to preterm delivery (Professional consensus). Uterine contractions can be detected by the cardiotocometry and by the patient herself. Uterine contractions frequency does not reliably predict spontaneous preterm birth (NP3). Cervical modifications may be appreciated by ultrasonographic measurement of cervical length and vaginal examination (Bishop score). Cervical length is significantly correlated with the risk of spontaneous preterm birth (NP1). The 15 and 25mm thresholds are the most relevant to respectively predict and rule out spontaneous premature birth at 48hours and 7 days (professional consensus). In symptomatic patients, routine ultrasonographic measurement of cervical length at admission is not associated with a significant reduction of spontaneous preterm birth rate (NP3). Clinical evaluation of the cervix (Bishop score) by vaginal examination is an effective parameter for the prediction of preterm birth (NP2). The higher the Bishop score, the higher the risk of preterm birth (NP3). It is not possible to recommend the use of a tool more than another (cervix ultrasound versus vaginal examination) in women experiencing preterm labor (grade B). However, due to the excellent negative predictive value of cervical ultrasound measurement and the lower interobserver variability, we suggest to perform a cervical ultrasonographic measurement before an in utero transfer for preterm labor (professional consensus). Screening for fetal fibronectin in the genital tract of patients with preterm labor has an excellent negative predictive value for predicting the absence of spontaneous preterm birth at 48hours and 7 days (NP2). Nevertheless, its use in symptomatic women is not associated with a reduction of preterm birth rate (NP2) and is therefore not recommended (professional consensus).

Predictors of preterm birth in women with preterm labor are effective but do not allow a reduction of the preterm birth rate. The high negative predictive value of these predictors (Bishop score, ultrasound measurement of the cervix, fetal fibronectin detection in the genital tract) is an asset in the choice of an appropriate management in women with preterm labor (in utero transfer or corticosteroids).