Introduction
Prematurity is the leading cause of neonatal morbidity and mortality1, with severe emotional sequelae and high economic costs. Nowadays, the Preterm Birth (PTB) rate is 10.6% worldwide and 11.2% in Brazil, higher than suggested by the World Health Organization2,3. There are 15 million PTBs each year and the burden is directly associated with gestational age at birth.
To prevent PTB bad outcomes, studies have focused on identifiable risk factors such as having a short cervix. Early uterine cervical shortening in the second trimester is an important risk factor for prematurity4 and is associated with spontaneous preterm birth (sPTB). Thus, cervical length (CL) measurement during the second trimester could be used as a tool to identify women at risk of premature delivery 5.
Transvaginal ultrasound (TVU) performed during the second trimester can evaluate cervical shortening before labor and then a universal screening test has been proposed 6. Nevertheless, the CL cutoff point related to PTB is still in debate. Most studies consider CL ≤25mm as a risk factor, whereas others consider higher or lower cutoff points7–9.
Predicting PTB among pregnant women is the key to preventive interventions10. Thus, the aim of this study is to identify the association between CL at 18–22(+6) weeks of pregnancy and gestational age at birth in asymptomatic Brazilian women with singleton pregnancy and to assess the performance of TVU as a screening test to predict PTB.