Self-check, 3 steps
How to check
Lie on your back with knees bent, feet flat. Lift just your head and shoulders, do not do a full sit-up. Press your fingers horizontally across your midline, from just above your navel to just below.
1
Find the gap
Press 2–3 fingers horizontally across your midline. Feel for a soft space between the two sides of your rectus abdominis. How many fingers fit in the gap?
Gap width:
2
Feel for depth and tension
A gap that feels firm, you can feel resistance when you press, is functionally better than a gap that feels soft and spongy, even if the width is similar. Width alone doesn't tell the whole story.
Tension:
3
Note any doming or coning
Look at your midline as you lift. Does the skin ridge up in a point or cone shape? Doming during any exercise means the load is exceeding what your linea alba can manage right now, a PT can help you modify.
Doming:
Compared to your early postpartum baseline
The self-check method above is consistent with clinician-taught assessment used by pelvic floor physical therapists. It cannot replace hands-on evaluation. Gap width of 2+ fingers with soft tension or active doming warrants PT assessment regardless of how the gap compares to your baseline. Source: Lee DG, Hodges PW. Behavior of the linea alba during a curl-up task in diastasis rectus abdominis. J Orthop Sports Phys Ther, 2016.