To evaluate the value of measurement of inter-rectus distance (IRD) by two-dimensional ultrasound and shear wave elastography (SWE) in quantitative evaluation of rectus abdominis elasticity in the diastasis recti abdominis.

Thirty-six parturients who underwent prenatal examination and full-term delivery at the First Affiliated Hospital of Guangdong Pharmaceutical University from March to December 2019 were selected as a study group, and 36 infertile women were recruited as a control group. Two-dimensional ultrasound was used to obtain IRD at the umbilical level, 5 cm above the umbilical level, and 5 cm below the umbilical level. SWE was used to quantitatively evaluate Young's modulus of bilateral rectus abdominis at the same levels [average (Emean), maximum (Emax), and minimum (Emin)]. The control group was examined by three physicians who had experience of＜10 years, 10~20 years, and＞20 years, respectively. One-way ANOVA was used to analyze the differences of IRD and SWE parameters obtained by ultrasound doctors with different working years. In the study group, different levels of IRD and SWE were measured and evaluated in the third trimester and 6-8 weeks postpartum, and two independent samples t-test were used for statistical analysis to compare their differences in the third trimester and 6-8 weeks postpartum.

In the control group, there was no significant difference in IRD or SWE parameters at the umbilical level, 5 cm above the umbilical level, and 5 cm below the umbilical level among the three doctors whose had experience of＜10 years, 10~20 years, and＞20 years (P＞0.05). Measurement of late pregnancy and postpartum IRD in the study group showed the following: IRD₀＞IRD₊₅＞IRD_-5, IRD₀ (3.00±0.53) cm, IRD₊₅ (2.87±0.57) cm, and IRD_-5 (2.53±0.33) cm at late pregnancy; and IRD₀ (2.39±0.54) cm, IRD₊₅ (2.09±0.31) cm, and IRD_-5 (1.96±0.25) cm at 6-8 weeks postpartum. The results showed that the measured values of IRD at different umbilical levels at 6-8 weeks postpartum were significantly lower than those at late pregnancy (t=2.965, 3.791, and 4.226, respectively; P＜0.001). Comparison of the mean values of SWE parameters of rectus abdominis muscle in the study group showed that the SWE parameters (Emean, Emax, and Emin) of the left and right bilateral rectus abdominis at late pregnancy were significantly lower than those at 6-8 weeks postpartum (P＜0.001).

Two-dimensional ultrasonic measurement of the distance between the rectus abdominis and real-time SWE can provide multi-dimensional scientific evidence for diastasis recti abdominis. Two-dimensional ultrasound combined with real-time SWE is simple and convenient to operate, and may become a routine method for comprehensive evaluation of the degree of abdominis separation and the clinical effect of abdominis separation in the late pregnancy and early postpartum.