Comparison of the inter-recti distance in nulliparous women measured in supine and standing positions using ultrasound imaging.

In physiotherapy for pregnancy-related diastasis recti abdominis, the inter-recti distance (IRD) measurement using ultrasound imaging is typically performed with the patient in supine position. Recently, a standing position, which is considered a functional body position, has been proposed for measurement. However, before adopting standing examination as routine, it is important to study how the linea alba behaves in this position in healthy nulliparas. The main objectives of the study were to compare (1) IRD at two measurement sites between standing and supine positions, and (2) IRD between the two sites within each position. IRD measurements were taken using ultrasound imaging in 27 nulliparas, at the upper edge of the umbilicus (umbilical site) and midway between the superior umbilical border and the xiphoid process (umbilical-xiphoid site), in both supine and standing positions. Photographs were taken to monitor participants' standing posture. At the umbilical-xiphoid site, the mean IRD was greater when standing than when supine (p = 0.004); no significant difference was observed at the umbilical site (p = 0.07). The mean IRD at the umbilicus was greater than at the umbilical-xiphoid site (p = 0.00001). The IRD at the midpoint between the superior umbilical border and the xiphoid process changed when assuming the standing position, which was not observed at the superior umbilical border. The IRD was greater in the umbilical region compared to the area further away from the umbilicus cranially. Our findings provide baseline data for future research on symptomatic populations and for establishing normative IRD values in the standing position, which could aid in developing clinical guidelines for assessing diastasis recti abdominis.