# Low‐Field Magnetic Resonance Imaging of the Late Gestation Cervix and Birth Outcome Correlation: A Prospective Cohort Study

## TL;DR

This study uses low-field MRI and automated analysis to assess the cervix in late pregnancy and links cervical features to birth outcomes like caesarean section.

## Contribution

A novel automated system for MRI-based cervical assessment in late gestation and new insights into cervical phenotype's role in birth outcomes.

## Key findings

- Cervical and stroma volumes increase with cervical length, while os diameters and utero-cervical angle decrease.
- Cervical stroma volume increases with maternal age, and higher cervical volume is linked to increased caesarean risk.
- Automated MRI reconstructions and segmentations showed excellent quality and inter-rater agreement.

## Abstract

To use low‐field MRI to produce reconstructions and 3D models of the cervix and to automate measurements for correlation with demographics and birth outcomes.

Prospective cohort study.

KCL Advanced Imaging Centre, St Thomas's Hospital.

Late gestation (36‐41w) women attempting their first vaginal birth, recruited to the MiBirth study (n = 97).

Reconstructed images were produced from 2D T2‐weighted Turbo‐Spin‐Echo 2D sequences acquired with a 0.55 T Freemax MRI scanner. Segmentations and anatomical landmarks were automated using an in‐house 3D deep learning segmentation network, from which cervical 2D measurements and 3D volumes were generated.

Quality of reconstructed images and segmentations. Inter‐rater variability for cervical biometry. Correlation between cervical measurements, maternal demographics and birth outcomes.

Successful reconstructions were obtained for 92.9%; 84.9% were good quality. Excellent or good quality segmentations were obtained for all successful reconstructions (n = 99). Inter‐rater variability between automated and manual biometry was excellent or good for cervical measurements. Total cervical and stroma volumes significantly increased with cervical length (p < 0.01). Os diameters and utero‐cervical angle significantly decreased as cervical length increased (p < 0.001). Cervical stroma volume increased with maternal age (p = 0.02). Controlling for maternal age, an increased cervical volume was associated with an increased risk of caesarean section (OR 1.09, p = 0.04).

This is a novel, accurate automated system to assess MRI late gestation cervical biometry and volumetry. We have shown that the late gestation cervical phenotype may influence birth outcomes and provided a new mechanism for increased risk of caesarean with maternal age.