Cervical length in late second and third trimesters: a mixture model for predicting delivery

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Medical Imaging

Background:

• Cervical length (CL) is a key indicator in late pregnancy.
• Understanding CL distribution is crucial for predicting delivery outcomes.
• Previous studies have explored CL but lacked detailed survival models for spontaneous delivery.

Purpose of the Study:

• To analyze the distribution of cervical length (CL) in the late second and third trimesters.
• To develop survival models for predicting spontaneous delivery based on CL.
• To identify distinct cervical length subgroups and their associated delivery risks.

Main Methods:

• Cross-sectional study of 647 women with singleton pregnancies.
• Transvaginal ultrasonography for CL measurements between 24-40 weeks' gestation.
• Mixture model analysis to describe CL distribution; survival analysis for delivery probability.

Main Results:

• CL distribution is a mixture of two Gaussian distributions: short cervix (26.15%) and long cervix (73.85%).
• Women with a short cervix have a significantly higher probability of spontaneous delivery (HR, 1.807; P<0.001).
• Gestational age and CL Z-scores effectively predict spontaneous delivery in both subgroups.

Conclusions:

• Cervical length measurement in late pregnancy follows two distinct Gaussian distributions.
• Late second/third-trimester CL measurements are valuable for estimating spontaneous delivery probability.
• The developed survival models offer predictive insights into delivery timing based on cervical length.