[The current role of progesterone and cervical ultrasound in preventing the risk of preterm birth in the general population].

Cervical ultrasound has become a key examination for estimating the risk of preterm birth. Cervical length is directly correlated with the duration of pregnancy: the shorter the cervix, the higher the risk of preterm birth. Several large cohort studies, including one conducted in France, have shown that the introduction of a universal cervical length screening program during second-trimester ultrasound was associated with a reduction in the frequency of preterm births. Numerous randomized, placebo-controlled and open-label multicenter trials have investigated the efficacy of progestins in an attempt to reduce the risk of preterm birth among women with a short cervix detected in the second trimester. Seventeen alpha-hydroxyprogesterone caproate, a semi-synthetic progestin, has been disappointing, failing to reduce the risk of spontaneous preterm birth. In contrast, two large randomized, controlled trials conducted in the general population have shown that vaginal progesterone started between 19 and 24 weeks of gestation and continued until 34-36 weeks significantly reduced the risk of spontaneous preterm birth among asymptomatic women with a short cervix detected on second-trimester ultrasound. Moreover, medical-economic analyses are converging to show that universal cervical length screening with vaginal progesterone treatment is cost-effective. Thus, the performance of vaginal ultrasound in selecting a population at risk of premature delivery in the general population due to a short cervix, combined with the effectiveness of treatment with vaginal progesterone to reduce this risk in the case of a short cervix, justifies the implementation of such screening.