Diastasis recti happens when the band of connective tissue running down the center of your abdomen stretches and thins, allowing the two sides of your rectus abdominis (your “six-pack” muscles) to drift apart. A gap wider than 2 centimeters, roughly two finger-widths, is the clinical threshold. The condition is most common during and after pregnancy, but it also affects men, older adults, and even newborns.
How the Abdominal Wall Separates
Your left and right abdominal muscles are joined at the midline by a strip of dense connective tissue called the linea alba. Think of it as a seam holding two panels together. When sustained pressure pushes outward from inside the abdomen, that seam stretches and thins. If the force is strong enough or lasts long enough, the two muscle panels move apart instead of staying snugly side by side.
This isn’t a tear or a rupture. The tissue is still intact, just wider and thinner than it should be. That’s why the hallmark sign is a visible bulge or ridge along the midline of the belly, especially when you sit up or strain. The muscles themselves also thin and elongate over time as the gap widens.
Why Pregnancy Is the Most Common Cause
Two forces work together during pregnancy to create the perfect conditions for separation: hormones and mechanical pressure.
Your body produces a hormone called relaxin throughout pregnancy. Relaxin loosens muscles, ligaments, and joints so your body can accommodate a growing baby. It specifically makes the abdominal muscles more flexible, which is helpful for expansion but also leaves the linea alba more vulnerable to stretching. Estrogen and progesterone contribute to this overall tissue laxity as well.
At the same time, the expanding uterus pushes steadily outward against the abdominal wall for months. This sustained mechanical load gradually elongates and thins the connective tissue. The combination of hormonally softened tissue and relentless outward pressure is what makes pregnancy the leading cause of diastasis recti by a wide margin. In some cases, a baby positioned toward the front of the abdomen concentrates force on the linea alba rather than distributing it evenly, which accelerates the separation.
About 60% of women have diastasis recti at six weeks postpartum, according to a prospective study published in the British Journal of Sports Medicine that followed 300 first-time mothers. By six months, the prevalence drops to about 45%, and by 12 months it’s around 33%. So the gap narrows on its own for many women, but a significant number still have it a full year after delivery.
Risk Factors That Increase the Odds
Not every pregnant person develops diastasis recti, and the severity varies widely. Several factors raise the likelihood:
- Multiple pregnancies. Each pregnancy stretches the linea alba again, often before it has fully recovered from the last one. The tissue becomes progressively less resilient.
- Carrying multiples. Twins or triplets create more uterine volume and more outward pressure than a single baby.
- Large birth weight. A bigger baby means more sustained force against the abdominal wall in the final weeks of pregnancy.
- Maternal age. Connective tissue loses elasticity with age, so older mothers may be more susceptible.
- Petite frame. Less abdominal wall surface area to distribute the expanding pressure can mean more concentrated force on the linea alba.
Interestingly, that same British Journal of Sports Medicine study found that about a third of first-time mothers already had measurable separation by week 21 of pregnancy, well before the third trimester. The process starts earlier than most people expect.
Causes Beyond Pregnancy
Anything that repeatedly or chronically raises pressure inside the abdomen can cause or worsen diastasis recti. This is why the condition isn’t exclusive to pregnancy.
Men can develop it too, particularly those who do heavy lifting, are older, or have gone through significant weight fluctuations. Rapid weight gain, especially visceral fat stored deep in the abdomen, pushes outward on the abdominal wall in much the same way a growing uterus does. The timeline is slower, but the mechanical principle is identical.
Chronic coughing (from conditions like COPD or long-term smoking), repeated straining during constipation, and improper bracing during heavy exercise all generate spikes of intra-abdominal pressure. Over time, these repeated forces can widen the gap between the muscles. Obesity compounds the problem by keeping baseline abdominal pressure elevated even at rest.
Diastasis Recti in Newborns
Some babies, especially those born prematurely, are born with diastasis recti simply because their abdominal muscles haven’t fully developed yet. The gap is usually visible as a small bulge along the midline when the baby cries or strains. In infants, the condition resolves on its own as the muscles strengthen and grow, and it typically doesn’t require any treatment.
Do Certain Exercises Make It Worse?
There’s a widespread belief that exercises like crunches and sit-ups will widen the gap, and for years postpartum fitness advice revolved around avoiding them entirely. The reality is more nuanced. A randomized controlled trial published in the Journal of Physiotherapy found that a 12-week program including curl-ups and twisted curl-ups did not worsen the gap in postpartum women with diastasis recti. The exercises actually increased abdominal muscle strength and thickness without changing the inter-recti distance.
That said, any movement that creates a visible “coning” or “doming” along your midline during exertion is generating force your connective tissue may not be ready to handle. The issue is less about specific exercises being universally dangerous and more about whether your abdominal wall can manage the pressure a particular movement creates. This varies person to person and changes as you recover.
How to Check for It at Home
You can do a simple self-check by lying on your back with your knees bent. Place two or three fingers horizontally just above your belly button, pointing toward your feet. Slowly lift your head and shoulders off the floor, as if starting a crunch. You should feel the edges of your abdominal muscles tighten around your fingers. If two or more fingers fit into the gap without resistance, or if you feel a soft, open space rather than firm tissue, that suggests diastasis recti. Check at your belly button, a few centimeters above it, and a few centimeters below, since the gap isn’t always uniform along its length.
The width of the gap matters, but so does the depth and tension of the tissue. A two-finger gap with firm, springy tissue underneath is a different situation than a three-finger gap with no resistance at all. Both the width and the quality of the connective tissue factor into how much the condition affects your core stability and daily function.