Understanding what causes diastasis recti is no simple task. First, we need to be able to define it. A lot of people will have a lot of different definitions, but here’s my version:
A diastasis recti is the inadequate regulation of tension in the linea alba, resulting in a loss of connection between the left and right sides of the body, or between the ribcage and pelvis, or both.
This loss of connection results in an inefficient transfer of energy for a variety of daily activities, depending on the woman. It can be felt during a diastasis recti test as a combination of depth and width, where the depth is generally more important.
The question then becomes, what causes this loss of tension? I think the answer begins during pregnancy.
What causes diastasis recti during pregnancy?
During pregnancy, a woman produces hormones that cause increased laxity of her soft tissues. This is good for preparing for birth and for accommodating the size of a growing baby. However, these hormones do not discriminate among soft tissues by selecting only the ones needed for birth. Instead, they affect all soft tissues, including ligaments, tendons, and of course, the linea alba.
Furthermore, the uterus grows in size as the baby grows, and this puts more outward pressure on the abdomen. This pressure causes the muscles and the linea alba to stretch as a consequence.
Lastly, the posture of a pregnant woman changes as her belly grows out in front of her and her abs stretch ever farther. To some degree, she will end up increasing the curve of her lower back to counteract the forward weight shift caused by her belly. This change in posture also results in an increased pressure on her abdominal muscles and her linea alba.
As you can see, these factors in combination explain why all mothers who reach their due date will have a diastasis recti. However, for most mothers, this naturally occuring phenomenon will resolve on its own. The question is: what causes the ones that don’t resolve?
How to create tension in the linea alba
Let’s begin by understanding what happens when it goes right.
The linea alba is an aponeurosis, meaning it is a soft tissue that functions as the attachment point for wide, flat muscles. In the case of the linea alba, it is the attachment for 6 of the 8 abdominal muscles. Only rectus abdominis does not attach attach at the linea alba. Instead, it sits inside of a sheath (a different soft tissue structure) that is divided down its middle by the linea alba.
The other 6 muscles—external obliques, internal obliques, and transverse abdominis—attach on the left and right of the linea alba. Each pulls at a slightly different angle to perform a slightly different role. Imagine it like a game of tug-of-war in which no one wins. These 6 muscles have to balance each other out to create tension in the linea alba. If one, or multiple of them, are doing too little or too much, then the linea alba loses tension. And this loss of tension results in a decreased ability to transfer energy and a reduction in the stability the abs can provide.
What causes diastasis recti that resolves without treatment?
According to research, the diastasis found in all mothers at birth will naturally resolve in two-thirds of them by 12 months postpartum. We need more research to fully understand these differences, but here are my thoughts.
Davis’s law is a principle stating that soft tissue remodels according to the mechanical stresses placed on it. When applying Davis’s law to the linea alba, it follows that to induce appropriate stress, we need to recreate function in the 6 abdominals that attach to the linea alba. Just as the hormonal and mechanical changes that occur during pregnancy cause a stretching of the linea alba, the hormonal and mechanical reversals that occur postpartum have the potential to encourage the remodeling of the linea alba to a smaller size.
The goal isn’t that the linea alba return to its pre-pregnancy state. Rather, the goal should be to recreate adequate tension in the linea alba as needed for daily activities. However, if any of the 6 muscles contribute ineffectively, it would make sense that the linea alba would remain in a more stretched out state, resulting in less tension, and therefore, less function.
What causes diastasis recti that doesn’t resolve?
The honest answer is there is no one thing that causes diastasis recti. It is a compilation of factors, some of which we probably still don’t understand. Nonetheless, here are several factors that we do know influence diastasis recti resolution.
Breastfeeding causes the production of hormones that continue the soft tissue laxity of pregnancy. Because of this, breastfeeding usually decreases the ability to generate tension in the linea alba. It shouldn’t be a reason not to breastfeed, but it is a factor to consider. For most women, the ability to generate tension improves when breastfeeding ends.
Nutrition, hydration, and gut health
Everything, including the postpartum body, heals better with proper nutrition. We simply need the right nutrients in the right amounts to be able to grow and regenerate tissue. If vital functions don’t have what they need, they will take it from other places. Therefore, healing well requires healthy food choices.
As for hydration, sixty percent of the human body is water. We need good hydration for good healing. Water is the best source of water. Drink at least 64 ounces of it.
Bloating, constipation, and other gut related issues can cause regular distension of the abdomen. When this occurs, it keeps the abdominal muscles and the linea alba on a stretch similar to pregnancy. It also decreases the chances that a woman will want to contract her abs since this adds more pressure to a situation that already has too much. Both of these can prevent remodeling of the linea alba and regeneration of abdominal strength. Depending on the degree of symptoms, addressing gut health may be necessary for healing a diastasis.
All of the abdominal muscles play a role in active exhalation, meaning the expulsion of air when not at rest. Breathing down and expanding the rib cage outward in all directions on the inhale allows the best contraction of the abs on the exhale.
Other breathing patterns might begin with inhaling up into the neck and shoulders or down but only into the belly. Consequently, neither of these allow for a complete contraction of all of the abdominal layers, and as previously discussed, we need this to return efficient ab function and recreate linea alba tension.
Pelvic floor function
Because of its close proximity to the lowermost abs, pelvic floor function relates closely to lower ab function. If the pelvic floor is weak, odds are the lower abs are as well. Additionally, if there’s too much activity and clenching in the pelvic floor, this is often a substitution for weak abs.
Because there are 2 sides to each of the 4 ab muscles, there needs to be at least a relative amount of symmetry between left and right sides. Otherwise, the linea alba will lose tension.
Further, there needs to be reasonable balance between the 4 layers. Too much or too little strength in one layer relative to the others can result in changes to the rib cage or bends in the abdominal wall. Both of which will ultimately decrease strength of the muscles and tension in the linea alba.
Changes in posture alter the position of the rib cage and pelvis in space, and these changes affect the orientation and tension of the abdominal wall. Because there’s so much motion available in the trunk, variations in posture can create curves to the abdominal muscles that result in areas of decreased strength.
As an example, standing with the pelvis tilted forward, known as an anterior pelvic tilt, is very common in postpartum women. Because it elongates the abdomen, this posture, in particular, decreases abdominal strength and limits the ability to regain pre-pregnancy belly shape and linea alba tension.
Imbalances in the hips or feet
Along similar lines, imbalances in the strength or function of the hips and feet can cause changes in posture. These compensations will lead to the effects of posture described above.
Risk factors for diastasis recti
Pregnancy is a risk factor for diastasis recti. But beyond this, the research is unclear. It does not seem to be related to:
- pre-pregnancy body mass index (BMI),
- weight gain,
- baby’s birth weight; or
- abdominal circumference.
Nor does the research support an increased risk of diastasis recti due to:
- maternal age,
- hypermobility of the mother,
- delivery method,
- heavy lifting; or
- non-specific exercise.
As you can see, we need far more research to improve our understanding of diastasis recti. There are a lot of factors that can contribute to its development, and this is why understanding the specifics of an individual woman are so crucial for her success in treatment. What works for one woman will likely be different than what works for the next.