The prevalence and consequences of abdominal rectus muscle diastasis among Finnish women: an epidemiological cohort study

Purpose Post-pregnancy abdominal rectus diastasis (ARD) has raised attention in the field of surgery in recent years, but there is no consensus about when to consider surgery. Our aim was to find out what is the normal inter-rectus distance in fertile aged, female population in Finland and to examine whether there is a linea alba width that would predispose to diastasis-related problems after pregnancy. Methods For this prospective cohort study, women participating early pregnancy ultrasound in Helsinki University Hospital Department of Obstetrics and Gynecology during 1.1.2018-8.3.2019, were recruited. The width of linea alba was measured by ultrasound during the early pregnancy ultrasound. Symptoms were measured by questionnaire including Health-Related Quality of Life (RAND-36) and Oswestry Disability Index for back symptoms and disability. Results Linea alba width was measured in total of 933 women. The average inter-rectus distance (IRD) among nulliparous women was 1.81 +/- 0.72 cm. After one previous pregnancy, the average linea alba width was 2.36 cm +/- 0.83 cm and after more pregnancies 2.55 +/- 1.09 cm. There was a positive correlation between previous pregnancies and the increased linea alba width (p = 0.00004). We did not perceive any threshold value of linea alba width that would predispose to back pain or movement control problems in this cohort, in which severe diastasis (over 5 cm) was rare. Conclusion Mean inter-rectus distance in parous population exceeds stated normative values. Moderate ARD (3.0-5.0 cm) alone does not seem to explain low back pain or functional disability in population level. Severe post-pregnancy diastasis (over 5.0 cm) is rare.