<p>Among the various predictive markers for an increased risk of preterm birth, sonographic measurement of cervical length has established itself best. A short cervix in the second trimester is associated with an increased risk of premature birth. The measurement should be standardised with the presentation of five landmarks. Sludge is an additional independent risk factor for spontaneous preterm birth. In the high-risk population, cervical length measurement is recommended between 18 and 24 weeks of pregnancy, as evidence-based therapies are possible. Cervical measurement in pregnant women with premature contractions can help to identify those who have a relevant risk of premature birth and, on the other hand, avoid unnecessary treatment and hospitalisation. In recent years, several countries have been able to demonstrate a reduction in spontaneous premature births with the introduction of general screening, even in the low-risk population.</p>