Diastasis recti (DR) is a common condition during pregnancy where the rectus abdominis muscles, often called the “six-pack” muscles, separate from each other. This separation occurs along the midline of the abdomen, which is a natural physical adaptation to accommodate the growing fetus. The condition is caused by a combination of the increasing physical pressure from the expanding uterus and the softening effect of pregnancy hormones, like relaxin, on connective tissue. This temporary change in the abdominal wall structure does not inherently cause pain, but it can lead to weakness and affect core function.
Anatomy of the Abdominal Wall Separation
The abdominal wall is composed of several muscle layers, with the rectus abdominis being the outermost pair that runs vertically from the ribcage to the pelvis. These two parallel muscle strips are held together by a band of fibrous connective tissue known as the linea alba. The function of this muscle group is to support the trunk, assist in posture, and facilitate movement.
During pregnancy, the mechanical force of the expanding uterus pushes outward against the abdominal wall. Simultaneously, hormones like relaxin and estrogen soften the collagen fibers within the linea alba, making it more pliable. This dual pressure causes the linea alba to thin and widen, creating a gap between the left and right sides of the rectus abdominis. This widening defines diastasis recti.
Recognizing the Midline Bulge and Doming
The most recognizable sign of diastasis recti is a temporary bulge or ridge along the midline of the abdomen. This appearance is often referred to as “doming” or “coning” due to its distinct football or tent-like shape. It typically occurs when there is a sudden increase in intra-abdominal pressure, such as when a person moves from lying down to a seated position, coughs forcefully, or strains during a bowel movement.
The ridge forms vertically down the center of the belly, often extending above or below the navel, as internal organs push against the thinned linea alba. This doming is most noticeable in the second and third trimesters when the uterus is at its largest. The bulge is not permanent; it disappears immediately once the pressure is released and the abdominal wall relaxes. Feeling the area during this doming can reveal a softer, almost jelly-like texture in the center where the muscle separation has occurred.
Performing a Safe Self-Check During Pregnancy
A simple self-assessment can be performed to check for diastasis recti without excessive strain. Begin by lying on your back with your knees bent and feet flat on the floor. Place two or three fingers horizontally across your belly button, pointing toward your pelvis.
While supporting your head with one hand, gently lift your head and shoulders a few inches off the floor, as if starting a small crunch. This minimal lift is enough to engage the rectus abdominis muscles. Press your fingers gently but firmly into the midline space to feel for the edges of the muscle on either side and note the width of the gap.
The separation is measured by the number of fingers that fit comfortably between the muscle edges. You should check for the gap width and depth both at the navel and a few inches above and below it, as the separation can vary. If you feel a gap wider than two finger-widths, or if your fingers sink deeply, consult a healthcare provider for confirmation.
Diastasis Recti vs. Normal Pregnancy Changes
It is important to distinguish diastasis recti from the general outward expansion and discomfort that are normal parts of a growing pregnancy. General outward pressure is a uniform distension caused by the volume of the growing uterus. In contrast, DR is specifically a vertical, midline bulge that is most evident when the abdominal muscles are activated and under pressure.
The condition also differs significantly from an abdominal hernia, though both involve a bulge. Diastasis recti is a muscle separation where the connective tissue is stretched but intact, with the bulge being abdominal contents pressing against the thinned linea alba. A hernia, such as an umbilical hernia, involves a true defect or hole in the abdominal wall through which internal tissue protrudes, requiring different management. DR becomes most visible around the late second or early third trimester, whereas general bloating and a full feeling are common throughout the entire pregnancy.