Objectives: To determine the measures to prevent spontaneous preterm birth (excluding preterm premature rupture of membranes)and its consequences.
Materials and methods: The PubMed database, the Cochrane Library and the recommendations from the French and foreign obstetrical societies or colleges have been consulted.
Results: In France, premature birth concerns 60,000 neonates every year (7.4 %), half of them are delivered after spontaneous onset of labor. Among preventable risk factors of spontaneous prematurity, only cessation of smoking is associated to a decrease of prematurity (level of evidence [LE] 1). This is therefore recommended (grade A). Routine screening and treatment of vaginal bacteriosis in general population is not recommended (grade A). Asymptomatic women with single pregnancy without history of preterm delivery and a short cervix between 16 and 24 weeks is the only population in which vaginal progesterone is recommended (grade B). A history-indicated cerclage is not recommended in case of only past history of conisation (grade C), uterine malformation (Professional consensus), isolated history of pretem delivery (grade B) or twin pregnancies in primary (grade B) or secondary (grade C) prevention of preterm birth. A history-indicated cerclage is recommended for single pregnancy with a history of at least 3 late miscarriages or preterm deliveries (grade A).). In case of past history of a single pregnancy delivery before 34 weeks gestation (WG), ultrasound cervical length screening is recommended between 16 and 22 WG in order to propose a cerclage in case of length<25mm before 24 WG (grade C). Cervical pessary is not recommended for the prevention of preterm birth in a general population of asymptomatic women with a twin pregnancy (grade A) and in populations of asymptomatic women with a short cervix (Professional consensus). Although the implementation of a universal transvaginal cervical length screening at 18-24 weeks of gestation in women with a singleton gestation and no history of preterm birth can be considered by individual practitioners, this screening cannot be universally recommended. In case of preterm labor, (i) it is not possible to recommend one of the methods over another (ultrasound of the cervical length, vaginal examination, fetal fibronectin) to predict preterm birth (grade B); (ii) routine antibiotic therapy is not recommended (grade A); (iii) prolonged hospitalization (grade B) and bed rest (grade C) is not recommended. Compared with placebo, tocolytics are not associated with a reduction in neonatal mortality or morbidity (LE2) and maternal severe adverse effects may occur with all tocolytics (LE4). Atosiban and nifedipine (grade B), contrary to betamimetics (grade C), can be used for tocolysis in spontaneous preterm labour without preterm premature rupture of membranes. Maintenance tocolysis is not recomended (grade B). Antenatal corticosteroid administration is recommended to every woman at risk of preterm delivery before 34 weeks of gestation (grade A). After 34 weeks, evidences are not consistent enough to recommend systematic antenatal corticosteroid treatment (grade B), however, a course might be indicated in the clinical situations associated with the higher risk of severe respiratory distress syndrome, mainly in case of planned cesarean delivery (grade C). Repeated courses of antenatal corticosteroids are not recommended (grade A). Rescue courses are not recommended (Professional consensus). Magnesium sulfate administration is recommended to women at high risk of imminent preterm birth before 32WG (grade A). Cesarean is not recommended in case of vertex presentation (Professional consensus). Both planned vaginal or elective cesarean delivery is possible in case of breech presentation (Professional consensus). A delayed cord clamping may be considered if the neonatal or maternal state so permits (Professional consensus).
Conclusion: Except for antenatal corticosteroid and magnesium sulfate administration, diagnostic tools or prenatal pharmacological treatments implemented since 30 years to prevent preterm birth and its consequences have not matched expectations of caregivers and families.
Keywords: Cerclage; Cervical pessary; Corticosteroid; Corticoïdes; Fetal fibronectin; Fibronectine; Longueur échographique du col; Magnesium sulfate; Pessaire; Preterm birth without preterm premature rupture of membranes; Progesterone; Progestérone; Prématurité spontanée à membranes intactes; Sulfate de magnésium; Tocolyse; Tocolysis; Ultrasound cervical length.
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