What's Actually Going On
The linea alba is the fibrous seam joining your left and right "six-pack" muscles down the midline. During pregnancy the growing uterus stretches and thins it, and the muscles drift apart sideways. This is a normal adaptation, not a tear and not a hernia.
Here's the part that gets missed: how your abdominal wall works depends on the muscles generating tension across a competent seam, not on the absolute width of the gap. A narrow gap with a slack, doming midline can be more of a problem than a slightly wider gap that holds tension well. That's why the best trials show strength and function improving while the measured gap barely moves.
How to Identify It
There's no high-accuracy "special test" for diastasis, because it's a measurement of a distance, not a provocation of a pathology. The skill is measuring consistently and, more importantly, judging midline tension and doming.
- Palpation on a head-lift, in finger-widths no validated accuracy
- Calipers — more repeatable than fingers, still examiner-dependent measurement tool
- Ultrasound — the most reliable and valid method where available reference standard
Always palpate for a discrete hernia defect, and screen any back pain or leaking as their own problems rather than blaming the gap.
The Debate
Folklore: "Never do crunches, they split the abs wider."
Blinded RCT (Gluppe 2023, N=70): curl-ups improved strength without worsening the gap. Doming during a rep is a coaching cue, not proof of harm.
Folklore: "Stop training your abs in pregnancy to protect the midline."
RCT (Bø 2024, N=96): abdominal + pelvic-floor training in pregnancy did not increase the gap. Safe to keep training.
Belief: "The gap weakens your core and causes back pain and leaking."
Two reviews (over 5,000 women): no consistent link between the gap and back pain or leaking. Treat those separately.
Claim: "Conservative exercise fixes the gap."
Meta-analyses agree exercise beats nothing, but the effect is small (a few millimetres) with low certainty. Set expectations: function improves more reliably than the gap closes.
There is no single MSK physiotherapy guideline for diastasis. NICE NG210 (2021) addresses it within pelvic-floor guidance and says supervised exercise is unlikely to worsen it; the only formal consensus is surgical (Italian Delphi, 2025).
Honest Limitations
The studies measure millimetres, you feel function
Nearly every trial optimises the gap width. Patients come in for bulging, weakness, appearance, and confidence. A few-millimetre change can be statistically real and completely invisible to the person living in the body.
The "right" dose was never established
No trial pins down the optimal load, sets, or progression. Real-world adherence to home programs is lower than in studies and rarely verified, so prescription is educated extrapolation.
Everyone measures it differently
Different cutoffs (2 vs 3 cm), sites (above vs below the navel), and tools (fingers vs calipers vs ultrasound) mean studies are measuring different things and calling them the same condition. That's why certainty stays low even with 34 trials.
The Nuance
Surgery vs conservative. Most women don't need surgery. The gap commonly narrows on its own early, function responds to loading, and the things people fear most (back pain, leaking) aren't reliably caused by it.
Surgery (stitching the midline back together, sometimes with mesh) is a reasonable, effective option for the minority left with a large, symptomatic gap after genuinely trying conservative care, or when a true hernia needs repair. Consensus surgical thresholds run from greater than 2.5 cm (symptomatic) up to 5 cm at the widest point. Which surgical technique is best is still an open debate.
