Quantitative Evaluation of Pubic Symphysis in Late Pregnancy Using T2* Mapping

Background: T2* mapping is a reliable tool in articular cartilage imaging. It has been widely used to evaluate the degeneration of knee joint and intervertebral discs. Degenerative joint disease of pubic symphysis is the primary cause of groin pain during late pregnancy. Objectives: To evaluate the alterations of pubic symphyseal cartilage during late pregnancy using T2* mapping. Patients and Methods: Sixty-one first-pregnancy women, 48 second-pregnancy women and 64 nulliparous women were enrolled in this case-control study. All subjects underwent MRI exam of the pubic symphysis on a 1.5T MR scanner, including T2* mapping sequence. Regions of interest (ROIs) were hand-drawn on T2* maps along the left and right side of the cartilage and anterior/middle/posterior sub-regions of each side. T2* values were analyzed and compared among the three groups using analysis of variance. The average pubic symphyseal width was measured. The correlation between pubic symphyseal width and T2* values of cartilage were analyzed using Pearson's correlation coefficient. Results: Compared with nulliparous women, T2* values increased significantly in late pregnancy in the left/right cartilage of pubic symphysis. The differences were mainly driven by the posterior sub-region; while, no differences were found between women during first and second pregnancies. The positive linear correlation between symphyseal width and mean T2* values of the cartilage was only seen in the group of women during first pregnancy, with no significant linear correlation in the other two groups. Conclusion: T2* mapping is a sensitive quantitative method capable of detecting changes in the pubic symphyseal cartilage related to pregnancy, and the T2* values increased significantly during late pregnancy.