Intra- and Interimage Reliability of Inter-Rectus Distance Measurements Determined via Ultrasound Imaging by the Same or Different Testers in Women in the Early Postpartum Period.

OBJECTIVES: No consensus regarding the optimal position and location for the measurement of the inter-rectus distance (IRD) via ultrasound (US) has been reached. By investigating the intra- and interimage reliability of IRD measurements taken in different positions and at different locations within and between testers, this study provides a theoretical basis for the current situation.

METHODS: The IRD was measured via US in 46 women at 42-60 days after delivery at the superior margin of the umbilicus and 3 cm above, 5 cm above and 3 cm below the umbilicus while the women were in the supine, crunch and standing positions. In the interimage test, every participant was tested 2 times by Physician X and 1 time by Physician Y; in the intraimage test, the images collected by Physician X during the first test were saved in the machines, and two measurements were performed by Physician X and one measurement was performed by Physician Y. Paired t tests and intraclass correlation coefficients (ICCs) were calculated.

RESULTS: Only the first IRD measurements by tester X and tester Y at 3 cm below the umbilicus in the crunch position were significantly different (9.56 ± 6.00 versus 11.00 ± 5.55) (P < .05). All the ICCs were greater than .75, and the intratester ICCs were greater than or equal to the corresponding intertester ICCs. The ICCs at 3 cm below the umbilicus were the smallest in the supine and crunch positions and the largest in the standing position due to the increased frequency of IRD values of 0. The ICCs for the crunch position were greatest according to the intraimage test but smallest according to the interimage test. The interimage ICCs between the two testers in the supine position at the superior margin, 3 cm above, 5 cm above, and 3 cm below the umbilicus were .972, .974, .975, and .956, respectively.

CONCLUSIONS: Ultrasound imaging (USI) is a reliable method for measuring the IRD in women in the early postpartum period. The dynamic measurement of the IRD at or above the umbilicus in the supine position by different testers in real time showed the highest reliability.