# Sonographic Evaluations of the Pubic Symphysis at Different Stages of Pregnancy

## TL;DR

This study uses sonography to measure changes in the pubic symphysis during pregnancy and finds correlations with fetal and maternal weight.

## Contribution

The study introduces a new sonographic parameter called 'pubic symphysis entry' and identifies its correlation with fetal weight.

## Key findings

- Pubic symphysis width is most consistent and correlates with fetal weight.
- Depth of the pubic symphysis shows the highest variability during pregnancy.
- Maternal weight and weight gain are strongly associated with pubic symphysis measurements.

## Abstract

Background/Objectives: The pubic symphysis is formed by the fusion of the right and left pubic bones. The metrics, such as breadth, length, and depth, increase during pregnancy and can be measured and analyzed using standard sonography. Obstetricians require clear and consistent criteria for standard sonography evaluation. Methods: Sonographic examinations were performed on a cohort of 225 pregnant women, aged between 23 and 41 years, as part of a prospective observational study. The parameters measured included pubic symphysis entry middle width, intertubercular distance, pubic symphysis width, and pubic symphysis depth. Results: The width of the pubic symphysis exhibited the greatest consistency, measuring between 2.2 and 11.3 mm, whereas the depth displayed the highest variability, ranging from 5.4 to 22.6 mm. The measurements most correlated with fetal weight included pubic symphysis entry width (6.5 ± 3.4 mm; p ˂ 0.001), pubic symphysis width (6.4 ± 2.9 mm; p ˂ 0.001), and depth (14.8 ± 4.8 mm; p = 0.03). The intertubercular distance exhibited the strongest correlation with maternal age (15.1 ± 5.4 mm; p = 0.03). In contrast, pubic symphysis entry width (6.4 ± 3.3 mm; p = 0.02; 6.4 ± 3.4 mm; p ˂ 0.001) and pubic symphysis width (6.3 ± 2.6 mm; p = 0.01; 6.3 ± 2.6; p ˂ 0.001) demonstrated stronger associations with maternal weight and weight gained during pregnancy, respectively. In the singular pregnancy group, the width of the pubic symphysis exhibited significant correlations with fetal weight categories: under or equal to 1000 g (4.56 ± 1.5 mm; p = 0.02), 1001–2000 g (5.51 ± 2.6 mm; p = 0.02), and more than 3000 g (7.3 ± 3.9 mm; p = 0.02). Pubic symphysis entry width is significantly correlated with fetal weight in the range of 1001–2000 g (5.5 ± 3 mm; p = 0.02) and fetal weight exceeding 3000 g (7.4 ± 3.9 mm; p = 0.02). In singular pregnancies, statistically significant differences were noted in intertubercular distance (15.9 ± 7.2 mm vs. 13.4 ± 6.2 mm; p = 0.03) when comparing fetuses weighing 2000 g or less between nulliparous and multiparous women. Conclusions: Fetal and maternal weight were the primary parameters that were positively correlated with these measurements. The term ‘pubic symphysis entry’ is proposed to describe a trapezoidal space situated superior to the pubic symphysis disc, delineated by an imaginary line connecting the bilateral pubic tubercles.