Cervical length distribution among Brazilian pregnant population and risk factors for short cervix: A multicenter cross-sectional study.

Objective: Since there are populational differences and risk factors that influence the cervical length, the aim of the study was to construct a populational curve with measurements of the uterine cervix of pregnant women in the second trimester of pregnancy and to evaluate which variables were related to cervical length (CL) ≤25 mm.

Materials And Methods: This was a multicenter cross-sectional study performed at 17 hospitals in several regions of Brazil. From 2015 to 2019, transvaginal ultrasound scan was performed in women with singleton pregnancies at 18 0/7 to 22 6/7 weeks of gestation to measure the CL. We analyzed CL regarding its distribution and the risk factors for CL ≤25 mm using logistic regression.

Results: The percentage of CL ≤ 25mm was 6.67%. Shorter cervices, when measured using both straight and curve techniques, showed similar results: range 21.0-25.0 mm in straight versus 22.6-26.0 mm in curve measurement for the 5th percentile. However, the difference between the two techniques became more pronounced after the 75th percentile (range 41.0-42.0 mm straight x 43.6-45.0 mm in curve measurement). The risk factors identified for short cervix were low body mass index (BMI) (OR: 1.81 CI: 1.16-2.82), higher education (OR: 1.39 CI: 1.10-1.75) and personal history ([one prior miscarriage OR: 1.41 CI: 1.11-1.78 and ≥2 prior miscarriages OR: 1.67 CI: 1.24-2.25], preterm birth [OR: 1.70 CI: 1.12-2.59], previous low birth weight <2500 g [OR: 1.70 CI: 1.15-2.50], cervical surgery [OR: 4.33 CI: 2.58-7.27]). By contrast, obesity (OR: 0.64 CI: 0.51-0.82), living with a partner (OR: 0.76 CI: 0.61-0.95) and previous pregnancy (OR: 0.46 CI: 0.37-0.57) decreased the risk of short cervix.

Conclusions: The CL distribution showed a relatively low percentage of cervix ≤25 mm. There may be populational differences in the CL distribution and this as well as the risk factors for short CL need to be considered when adopting a screening strategy for short cervix.