Introduction
Preterm birth (PTB) is one of the most important causes of perinatal morbidity and mortality1, occurring in 7-11% of all deliveries2. Despite its high prevalence, there are no accurate prediction models to identify women at high-risk for PTB, partly due to the multifactorial etiology of PTB3.
Cervical length (CL) has been historically linked to PTB. Ultrasound is the most commonly used tool to assess CL for early detection of PTB4. Occurrence of a short cervix in the second trimester, frequently detected using transvaginal ultrasonography (TVS), was found to be a strong predictor of preterm birth5,6. A universal mid-trimester transvaginal cervical length screening tool may reduce the risk of preterm birth7. So far, whether CL values in the first trimester can predict PTB is controversial 8,9. In addition to CL, several other factors have been found to modify the risk of preterm birth, such as smoking and prepregnancy body mass idex10,11. Over the years, nomograms have become indispensable tools in clinical decision making. Therefore, we reasoned that the risk factors of PTB can be used to establish a prediction model to guide obstetricians in identifying patients at risk of PTB.
Thus, we searched for potential predictors of PTB < 37 weeks and 34 weeks in pregnant women with a short cervix and used these factors to establish nomograms.