Currently, there are not enough studies to evaluate the relationship between diastasis and pelvic floor muscle dysfunctions in postpartum women. The aim of our study was to determine the relationship of diastasis of the rectus abdominis muscles (DRAM) with pelvic floor muscle function, and size of hiatal area in postpartum women. For DRAM examination, the inter-rectus distance (IRD) was measured by a linear probe 2D ultrasonography (USG). Examination of the pelvic floor muscle function (PFM) was performed by manometry. Size of hiatal area was measured by 2D and 3D/4D transperineal USG.

The study was carried out in the period from April 2021 to April 2022. The power analysis to determine appropriate sample size was used. We used an estimate, based on a sample selection of participants, based on a test power of 0.80 and an alpha of 0.05 (type I error). There were 180 births in the observed period, and the expected prevalence of diastasis was 30%; therefore, we needed at least 116 women to participate in the study. 
	Examination of DRAM–IRD distance was measured with a linear probe 2D USG at 4.5 cm above the navel, in the navel area, and 4.5 cm below the navel. Participants were supine and examined at rest (without load), as well as with lower limbs elevated (with load). The degree of severity was classified into four degrees. Grade 1 = moderate, IRD width 2.1–3 cm; grade 2 = medium, IRD width 3.1–5 cm; grade 3 = severe, IRD width 5–7 cm; grade 4 = very severe, IRD width 7–9 cm.
	Pelvic floor muscle function was examined by manometer. We investigated the strength, endurance, and relaxation ability of the pelvic floor muscles. Maximum voluntary contraction (MvC) in cmH2O, MvC endurance in seconds, and pelvic floor muscle relaxation were measured.
	The morphometry of the pelvic floor muscles and size of hiatal area was examined by 2D and 3D/4D USG. Examination was performed with an empty bladder in the lithotomy position. The probe was placed longitudinally on the perineum. 2D and 3D/4D images were scanned at rest, during maximum contraction, and during the Valsalva manoeuvre in cm2, and antero-posterior dimension of the hiatus, as well as latero-lateral dimension of the hiatus, in cm. Anorectal angle and levator plate angle images were also taken.
      Inclusion criteria
Women from 6 weeks to up to 6 months after birth and over 18 years old were included.
      Exclusion criteria
The following comprise the exclusion criteria: psychiatric illness, postpartum depression, non-cooperation, neurological disease conditions after a stroke, a history of brain injury, significant visual and hearing damage confirmed by neurological examination, serious internal, orthopaedic, or oncological diseases, abdominal surgery, disagreement with inclusion in the study, and ongoing physiotherapy for diastasis and pelvic floor dysfunction.

The observational prospective study included 150 women from 6 weeks to 6 months postpartum, with a mean age of 33.1 years. The final group consisted of 118 women. Thirty-two women were eliminated, for a loss of 21.3%. Two were excluded for obesity, five were not examined because of menstruation, 10 were excluded for ongoing postpartum physiotherapy, and 15 women did not show up for examination.
    DRAM: the average distance of the IRD at rest was 2.69 cm above the navel, 2.21 cm in the navel area, and 1.28 cm below the navel. During the load test, the average IRD distance was 2.61 cm above the navel, 2.61 cm in the navel area, and 1.75 cm below the navel. These measures indicated moderate DRAM.
   PFM: Pelvic floor muscle strength (MvC) was, on average, grade 2 cmH2O and duration of MvC was 3.76 seconds. These measures indicated slightly decreased function of pelvic floor muscles.
  The morphometry of the pelvic floor muscles and size of hiatal area: The average values of the anorectal angle in degrees were 122.13 at rest, 109.98 during contraction, and 119.84 during the Valsalva manoeuvre. The average values of the angle of the levator plate in degrees were 40.64 at rest, 43.55 during contraction, and 23.05 during the Valsalva manoeuvre. The average distance between the symphysis and the anorectal angle in cm was 4.33 at rest, 43.55 during contraction, and 5.23 during the Valsalva manoeuvre.
    According to the correlation analysis, we identified mild significant correlations of DRAM with the pelvic floor muscle MvC (r = -0.278**) and its duration (r = -0.274**). No correlation was found between DRAM and pelvic floor muscle morphometry and size of hiatal area by 2D or 3D/4D USG. (Table 1).

A moderate relationship was found between diastasis of the rectus abdominis muscles and pelvic floor muscle dysfunction. A relationship between the diastasis of the rectus abdominis muscles and size of hiatal area was not found. We believe this is due to the slight decrease in pelvic floor muscle strength and endurance, and because size of urogenital hiatus was normal.

A moderate relationship between diastasis rectus abdominis and pelvic floor muscle dysfunction was found. For clinical practice, this study implie that physiotherapist should inform the patients with DRAM to complete an exercise program for DRAM reduction and for  pelvic floor muscle strength and endurance .

Neurourol Urodyn. 2017 Mar;36(3):716-721