During pregnancy, the whole abdominal wall expands and also the fascia (linea alba) between the abdominal muscles widens, when the growing uterus and child stretch the abdominal wall. After giving birth, the changes are usually reversed roughly one year later.
In some women, the linea alba and the fascia layer do not return back to normal. Instead, a wide separation between the muscles, or diastasis, can cause back symptoms or a hernia. This separation has usually been treated with physiotherapy, but it is not enough to alleviate the symptoms for everyone.
In her doctoral thesis, plastic surgeon Reetta Tuominen investigated how the abdominal wall recovers from pregnancy and what the normal distance is between the abdominal muscles among women who have or have not given birth. The inter-rectus distance of nearly 1,000 women was measured in conjunction with an ultrasound carried out during pregnancy, and this monitoring was supplemented with a survey. Tuominen also examined the impact of rectus diastasis surgery on women’s quality of life and functional capacity.
“Rectus diastasis has become an increasingly common topic of discussion, and people have become more active in seeking restorative surgery. However, information on the effects of the phenomenon as well as the benefits and adverse effects of surgical treatment has been thin on the ground,” Tuominen says.
The study found that, already after one pregnancy, the distance in the middle of the straight abdominal muscle was approximately 2.5 centimetres, which is enough to rate as separation. However, diastases ranging from two to three centimetres in width did not appear to have an effect on women’s quality of life or back-related symptoms.
“Such slight expansion of the connective tissue in the abdominal muscle is common, and expectant mothers don’t have to worry about it. Usually, such diastases don’t need to be fixed through surgery,” Tuominen says.
Surgery for severe diastasis improves quality of life
Diastases are classified as difficult if they are more than five centimetres wide. Such cases are rare: in Tuominen’s study, they were observed in 1.5% of women. Tuominen studied two diastasis surgery techniques, the PSUM mesh technique and the HELP abdominoplasty. In both techniques, the adverse effects were minor. Patients in the HELP group reported a significant improvement in their quality of life and a significant reduction in back pain.
Tuominen also investigated the functional capacity of women’s abdominal muscles, measured with a sit-up test. Before diastasis surgery, only a handful of patients from among 46 were able to complete the sit-up test, even though they had regularly exercised several times per week and received physiotherapy. A year after surgery, the mean score in the sit-up test was 11 repetitions in 30 seconds.
According to Tuominen, surgical treatment benefits particularly women with severe rectus diastasis.
“Restored functional capacity makes it possible to continue leisure time activities and helps in everyday things, such as standing and walking for long periods, as well as a painless life,” Tuominen says.
Reetta Tuominen, MD, will defend her doctoral thesis entitled "Rectus diastasis: epidemiology and operative treatment" on 17 March 2023 at 12.00 at the Faculty of Medicine, University of Helsinki. The public examination will take place in the Niilo Hallman room of the Park Hospital at Stenbäckinkatu 11. Docent Agneta Montgomery from Lund University will serve as the opponent and Virve Koljonen as the custos. The thesis is also available in electronic form through the Helda repository.
Reetta Tuominen, specialist in plastic surgery
University of Helsinki and HUS Helsinki University Hospital