Supplementary Material for: Longitudinal Changes of Subpubic Arch Angle throughout Pregnancy

Objective: The objective of this study is to assess whether the subpubic arch angle (SPA) changes throughout pregnancy. Materials and Methods: We recruited a group of nulliparous women in the first trimester of pregnancy. Each woman was assessed 3 times throughout pregnancy, once per each trimester, by measuring SPA using a recently described highly reproducible three-dimensional transperineal ultrasound (linear reconstruction with contrast enhancement technique; OmniView-volume contrast imaging). Repeated measures analysis of variance was used to study SPA changes during pregnancy. Results: Overall, 97 women were included in the final analysis. SPA increased progressively and significantly (F = 27.824, p < 0.001) from the first to the second trimester (121.8 ± 8.7 vs. 123.5 ± 8.4°, p = 0.01) and from the second to the third trimester (123.5 ± 8.4 vs. 125.3 ± 8.1°, p = 0.01). Conclusion: SPA width increases progressively but slightly during pregnancy. Although this finding is interesting, the extremely small difference detected is unlikely to be clinically significant.