Why Does My Ribcage Feel Wider After Pregnancy?

Your bra doesn't fit, your ribs sit wider, and nobody mentioned this would happen. A physiotherapist explains rib flare after pregnancy — and why it's a breathing problem before it's a shape problem.

Your bras don't fit, and not in the way you were warned about. The band is tight. Old jeans do up but the waistband sits differently. Standing side-on in a mirror, the lower ribs seem to sit out and forward, and your stomach looks softer than the amount of effort you're putting in would suggest.

Nobody mentions this one. Everyone hears about the pelvic floor and the abdominal separation; almost nobody hears that the ribcage changes too, and that it doesn't always change back on its own. It has a name — rib flare — and understanding it matters more than it sounds, because a flared ribcage quietly undermines core and pelvic floor work happening underneath it.

Why does my ribcage feel wider after pregnancy?

Because it genuinely widened, and the position can persist.

Over nine months, the growing uterus pushes upward on the diaphragm and the organs sitting beneath the ribs. The ribcage responds the way it's designed to — it expands outward and upward to make room. The lower ribs in particular rotate up and out. This is normal, necessary, and happens to essentially everyone.

The part that varies is what happens afterwards. Once the pressure from below is gone, some people's ribcages settle back toward their original resting position without any intervention. Some don't. The ribs stay parked in the expanded position, held there by the muscles that spent nine months learning to hold them that way — and by the breathing pattern that came with it.

Almost every postpartum body has some degree of rib flare. Whether it persists has a lot to do with how you habitually move and breathe, and not much to do with anything you did wrong.

What is rib flare, exactly?

Rib flare is when the lower ribs sit angled outward and upward at rest, rather than stacked down over the pelvis.

The clearest way to think about it is the shape of your torso. From a physiotherapy perspective, the deep core works as a three-dimensional canister — the diaphragm is the lid, the deep abdominals and back muscles are the walls, the pelvic floor is the base. That canister works best when the lid sits roughly parallel and stacked over the base.

When the ribs flare, the lid tips. The diaphragm above and the pelvic floor below are no longer facing each other. The walls — your deep abdominals — are attached to a ribcage sitting in a lengthened, outwardly rotated position, which means they're being asked to generate tension from a mechanically poor starting point.

This is why rib flare is a breathing problem before it's a shape problem. A flared ribcage restricts how well the diaphragm can descend, which changes how pressure moves through the canister, which changes what the pelvic floor and deep abdominals have to do about it.

Does rib flare go away on its own?

Sometimes. Often not entirely.

There isn't a clean statistic to offer here, and anyone giving you one is guessing. What's clear clinically is that some people resolve it without doing anything in particular, and others carry it for years — which is why it's common to see it in someone five years postpartum who assumed this was simply their new body.

The good news is the more useful finding: the resting position of the ribcage is not fixed. Bone shape doesn't change much, but the position the ribcage is held in is largely a soft-tissue and motor-control question, and those respond to the right stimulus. Many people see real change with consistent work on breathing and rib position, at any point postpartum.

Why does rib flare matter for my core and pelvic floor?

This is the part worth caring about, more than the bra fit.

It limits the diaphragm. With the ribs flared, the diaphragm can't fully descend on the inhale. You end up breathing higher — more chest, shoulders, and neck — and less into the lower ribs and back where you want it.

It weakens the deep abdominals mechanically. The oblique abdominals attach to the lower ribs. When the ribs sit flared, those muscles are held long and can't produce tension efficiently. You can do a great deal of core work in that position and get frustratingly little from it.

It changes pressure management. If the lid and the base aren't facing each other, pressure generated when you lift, cough, or exert doesn't distribute evenly — it tends to go forward into the abdominal wall or down into the pelvic floor. That is the mechanism behind doming, and it's often a contributing factor when leaking persists despite diligent work.

It can contribute to back and rib pain. A ribcage held in extension keeps the low back in extension too, which is a common thread in postpartum back pain.

The practical implication: if you've been doing core work consistently and getting very little back, rib position is one of the more common reasons why. The exercises may be fine. The container they're happening in isn't set up to let them work.

How do I know if I have rib flare?

Two general observations, offered as education rather than a diagnostic test:

The mirror check. Stand side-on, relaxed, not sucking in. Look at the line from the bottom of your sternum to your lower ribs. If the lower ribs visibly lift and angle forward and outward rather than following the line of your torso downward, that's flare.

The hands check. Lie on your back with knees bent. Place your hands on your lower ribs, thumbs pointing back, fingers along the rib margin. Notice the angle between your two hands. A noticeably wide angle, and ribs that feel like they're sitting up away from the floor rather than resting down, is consistent with flare. Then breathe in. If your chest and shoulders rise but almost nothing happens sideways under your hands, that's the breathing pattern that tends to travel with it.

Neither of these is a substitute for assessment, and neither tells you anything alarming. They're orientation.

What helps a flared ribcage after pregnancy?

The approach is about restoring position and breath, in that order — not strengthening harder.

1. Get the breath into the lower ribs and back. This is the foundation and it's the same work as diaphragmatic breathing. Breathing three-dimensionally into the lower ribs is what mobilises the ribcage from the inside.
2. Emphasise the full exhale. This is the piece people miss. The ribs return toward their resting position on the exhale, driven partly by the abdominals. Most people breathing in a flared pattern never fully exhale, so the ribs never get the cue to come down. A slow, complete exhale — longer than the inhale, all the way to empty — is doing more here than any abdominal exercise.
3. Stack the ribs over the pelvis. Standing, notice whether your ribs sit forward of your hips. Bringing them back over the pelvis, without tucking the tailbone or gripping the abdominals, is a position to practise until it stops feeling like effort.
4. Work in positions that discourage flare. Lying on your back with feet elevated, or anything that puts the ribs slightly down-rotated, makes it much easier to find the pattern. Overhead work and back-extended positions make it harder, so they're not where you start.
5. Add deep-core connection once the position is available. Only now does strengthening make sense, because now the abdominals have a mechanically useful starting position to work from.

Notice there's no taping, no bracing, and no sucking in. Holding the ribs down by gripping the abdominals looks like a correction and is actually just a different compensation — it restricts the breathing you're trying to restore.

Will my ribcage ever go back to how it was?

Possibly not exactly, and that's worth saying honestly. Pregnancy changes bodies, and some of those changes are permanent. Your ribcage may always be slightly wider than it was, and your old bra size may simply be your old bra size.

But "will it look identical" and "will it function well" are separate questions, and the second one is the one that affects how you feel. The position the ribcage rests in, how well your diaphragm moves, how your deep core generates tension, and whether pressure distributes well when you lift — all of those can change meaningfully, and they're the variables that determine whether you feel strong and steady. Chasing the exact pre-pregnancy silhouette is the less useful goal.

Where to start

If your ribs feel wide, your breathing sits high in your chest, and core work hasn't been delivering, the starting point isn't more core work. It's restoring the breath and the position underneath it — and then rebuilding in the right order.

That order is what the free 6-Week Postpartum Movement Roadmap lays out: what to do first, what to do next, and what to leave until later.

Frequently asked questions

This article is general education from a physiotherapist's perspective. It is not individualized physiotherapy advice, does not create a therapist-patient relationship, and is not a substitute for care from a licensed healthcare provider in your area. Harleen Kalra is a physiotherapist registered in British Columbia, Canada. For personalized assessment and treatment, please see a licensed pelvic-health provider where you live.