[Predictive tools of preterm birth in asymptomatic high-risk pregnancy].

Objective: Describe tools designed to predict preterm birth in asymptomatic high-risk pregnancy and determine their predictive value.
Methods: The PubMed database, the Cochrane Library and the recommendations from the French and foreign obstetrical societies or colleges have been consulted.
Results: Obstetric history particularly spontaneous preterm birth identifies a population at risk for preterm birth for the current pregnancy (LE3). This risk is related to the number of prior preterm birth and is even higher than the term of the prior event is more premature and that the event concerns the last pregnancy (LE3). The literature data are insufficient to recommend systematic cervical examination at each prenatal visit in asymptomatic high-risk pregnancy (multiple pregnancy, uterine malformations, history of spontaneous preterm birth, excisional cervical procedure or at least two voluntary first trimester abortion) (professional consensus). Regular recording of uterine activity and home visits for asymptomatic high-risk pregnancy did not predict nor reduce the risk of preterm birth (LE2) and are not recommended (grade B). In asymptomatic high-risk pregnancy, ultrasonographic measurement of cervical length estimates the risk of preterm birth (LE2). Shorter is the cervical length higher is the risk of preterm birth (LE3). In asymptomatic patient with prior preterm birth, ultrasonographic measurement of cervical length estimates the risk of preterm birth (LE2). The strategy of ultrasound indicated cerclage are discussed in dedicated chapter. The measurement of cervical length by transvaginal ultrasonography in asymptomatic pregnancy with uterine malformation, a history of cervical treatment, at least two voluntary abortions or having a multiple pregnancy would estimate the risk of preterm birth (LE3). A shortening of more than 10% of the cervical length at 3-week interval is associated with an increased risk of preterm birth (LE3). Systematic detection of fetal fibronectin is not recommended in asymptomatic high-risk population (grade C). The combination of ultrasound measurement of cervical length and fetal fibronectin detection improves modestly the prediction of preterm birth (LE3). However, literature data are insufficient to recommend routine measurement of cervical length by transvaginal ultrasonography during surveillance ultrasounds and/or detection of fetal fibronectin because this policy has never demonstrated its interest in preventing preterm birth and in the reduction of neonatal morbidity and mortality (professional consensus).
Conclusion: Several predictive tools are described to define the risk of preterm birth but there is no evidence to date of the effectiveness of systematic screening strategy on the prevention of prematurity in asymptomatic high-risk population, except the ultrasound measurement of the cervical length in the population of patients having had a prior preterm birth.
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