Correlation between Endocervical Length in the First Trimester and Spontaneous Preterm Delivery

Introduction: Prematurity is a public health problem in Brazil, with 12% of deliveries occurring before 37 weeks of gestation. The measurement of the cervix in the second trimester is already established as a method of screening for prematurity and some studies point out advantages to start this screening in the first trimester. Objective: To define the correlation between the length of the endocervix by transvaginal ultrasound in the first trimester (11 to 14 weeks) with spontaneous early deliveries. Method: A prospective and observational study realized in a suplementar and private ultrasound clinic and hospital of Porto Alegre, Brazil between 2019-2020. Ultrasound screening of cervix was performed in singleton pregnancies in first and second trimester of pregnancy and correlated with age of delivery. Results: 142 pregnant women were studied, 80% were in the first pregnancy. The average age was 33.8 years. The rate of prematurity was 18% before 37 weeks and 4% before 34 weeks. The average of cervix measured in the first and second trimesters in deliveries before 34 weeks was 32.7 mm and 29.3 mm, respectively. In term deliveries the median cervical length was 38.8 mm and 37.8 mm, respectively. When analyzing the measurements of the cervix in the second trimester, the cervix was smaller (p = 0.008) among deliveries below 34 weeks (29 mm) than deliveries after 37 weeks. No statistically related differences were found between preterm birth and first trimester cervix measurements. Conclusions: In this study, we did not observe a statistically significant relationship between first trimester cervix measurement and prematurity. More studies are needed to evaluate this finding. However, the measurement of the cervix in the second trimester is different from that found in the literature. This suggests a possible new cut-off point that increases the sensitivity of transvaginal ultrasound as a method of preventing prematurity.