Anatomy of the Linea Alba
The linea alba is a vertical band of connective tissue which runs from the base of the sternum, xiphoid process, to the pubic bone and divides the left and right Rectus abdominis muscles (i.e. the six-pack muscles). (1) This vertical band of connective tissue acts as an important attachment point for multiple muscles of the abdomen and inner core and functions to help maintain a certain degree of proximity between the abdominal musculature thus assisting with load transfer to enable a person to move, lift and carry with ease and to optimize function. The normal width of the Linea alba in nulliparous women, women who have not been pregnant, has been found to be up to 2.2 cm at a reference point 3 cm above the umbilicus (i.e. belly button). (5) There is currently no agreed upon normative range in parous women, women who have been pregnant, with there no current universally agreed-upon definition of mild, moderate and severe Diastasis Recti Abdominis. (Image Reference, 7)
Pregnancy and Postpartum Dysfunction of the Linea Alba
Linea alba directly translated from Latin means “white line” and is often visualized as a contoured groove in someone with well-defined abdominal muscles. This connective tissue does become “stretched” during pregnancy, to accommodate the growth of the fetus and supporting structures, with this a NORMAL adaptation to pregnancy. The research has shown that by 21 weeks gestation 33.1% of first-time pregnant women have a Diastasis Recti Abdominis (DRA). (3) During pregnancy with increase in abdominal circumference, associated with normal pregnancy weight gain, this “line” may become darker in color and known as the linea nigra (i.e. “black line) secondary to hormonal influence. (1) According to the literature at 6 weeks postpartum the prevalence of DRA is 60% with ~33% of women still exhibiting a DRA at 12 months postpartum. (2) There is currently no consensus with regards to the correlation of age, delivery mode and number of pregnancies to presence and/or severity of DRA. (4)
Hernia v. Diastasis Recti Abdominis
DRA can sometimes be confused with a hernia with the difference being with DRA there is an increase in distance between the Rectus abdominis musculature, measured as inter-recti distance (IRD), due to weakness and thinning of the Linea alba, BUT there is no defect in the connective tissue. With a ventral hernia, there is a defect or “tear” of the Linea alba which therefore causes visceral tissue, most commonly the small intestines, to herniate or “push through” the defect especially with increases in intra-abdominal pressure (i.e. sit-up, heavy lifting, straining with a bowel movement).
Is DRA Correlated with Low Back Pain Postpartum?
Per the literature, there is NO DIFFERENCE in reported low back pain in women with and without DRA 12 months postpartum. (2, 3) At this time, with the research we have available, we cannot definitively show causation with regards to the simultaneous presence of DRA and low back pain or even stress urinary incontinence. (6)
How Can a Pelvic Physical Therapist Help
If you find yourself experiencing any of the above symptoms, reach out to your local physical therapist for evaluation! Treatment is not a “one-size fits all” for it will be individualized to your specific symptom complaints and impairments noted upon completion of examination.
Pregnancy and postpartum can be a beautiful time during one’s life but can also be a time with associated fear of the unknown as your body physiologically changes to accommodate the growth of your unborn child. No matter if you are pregnant, immediately postpartum or 5+ years postpartum do not let this fear overcome you! Most of these anatomical adaptations are a normal part of the pregnancy and postpartum experience but a pelvic physical therapist has the knowledge, education and experience to educate you regarding your body and most importantly help you take back control of your body and your life!
References:
Linea alba (abdomen): Function, anatomy & conditions. Cleveland Clinic. (n.d.). Retrieved April 11, 2023, from https://my.clevelandclinic.org/health/body/23483-linea-alba
Goom, T., Donnelly, G. and Brockwell, E. (2019) Returning to running postnatal – guideline for medical, health and fitness professionals managing this population. [https://mailchi.mp/38feb9423b2d/returning-to-running-postnatal-guideline]
Sperstad, J. B., Tennfjord, M. K., Hilde, G., Ellström-Engh, M., & Bø, K. (2016). Diastasis recti abdominis during pregnancy and 12 months after childbirth: Prevalence, risk factors and report of Lumbopelvic Pain. British Journal of Sports Medicine, 50(17), 1092–1096. https://doi.org/10.1136/bjsports-2016-096065
Gluppe, S., Engh, M. E., & Bø, K. (2021). What is the evidence for abdominal and pelvic floor muscle training to treat diastasis recti abdominis postpartum? A systematic review with meta-analysis. Brazilian Journal of Physical Therapy, 25(6), 664–675.https://doi.org/10.1016/j.bjpt.2021.06.006
Beer, G. M., Schuster, A., Seifert, B., Manestar, M., Mihic-Probst, D., & Weber, S. A. (2009). The normal width of the linea alba in nulliparous women. Clinical Anatomy,22(6), 706–711. https://doi.org/10.1002/ca.20836
Braga, A., Caccia, G., Nasi, I., Ruggeri, G., Di Dedda, M. C., Lamberti, G., Salvatore, S., Papadia, A., & Serati, M. (2020). Diastasis recti abdominis after childbirth: Is it a predictor of stress urinary incontinence? Journal of Gynecology Obstetrics and Human Reproduction, 49(10), 101657. https://doi.org/10.1016/j.jogoh.2019.101657