Rib Pain in Pregnancy: Why It Happens and What Pilates Can Do

If you're deep in your second or third trimester and it feels like someone is pressing a thumb into your lower ribs every time you sit down, you are not imagining it and you are not alone. Rib pain in pregnancy is common, and most of the time it comes down to two things happening at once: the hormone relaxin is loosening the joints between your ribs and your breastbone and spine, and your uterus is simply running out of room below, so it pushes up against your rib cage from underneath. The good news is that this particular kind of ache responds well to a short, specific list of changes — mostly around how you breathe, how you sit, and which side you stretch — and Pilates happens to be built around exactly those tools.

Why Your Ribs Hurt in the First Place

Your rib cage is not one solid shell. It's a stack of joints — where each rib meets your spine in back and your breastbone in front — held together by ligaments that are designed to flex slightly every time you breathe. During pregnancy, relaxin loosens those ligaments the same way it loosens the joints in your pelvis, which is useful for the birth itself but means your ribs are more mobile, and sometimes more irritable, for months beforehand.

Layer on top of that the mechanical side: as your uterus grows, it eventually has nowhere to go but up, and by the third trimester it's often resting directly under your lower ribs. If your baby is head-down with feet tucked up near your ribs, a well-placed kick can turn background discomfort into a sharp, specific jab. Most people also develop a mild asymmetry — many of us already carry more tension on the right side, where the liver and a larger lobe of the diaphragm sit, and pregnancy posture changes tend to exaggerate whichever twist was already there, as trainers who specialize in prenatal fitness have described. That's part of why rib pain so often shows up on one side rather than both.

When It Needs a Closer Look

I want to say this clearly before anything else: most pregnancy rib pain is uncomfortable but not dangerous, and it usually eases once the baby drops lower or after delivery. But a few patterns are worth a same-day call to your midwife or OB rather than a Pilates fix. Pain specifically under the right ribs in the third trimester, especially paired with a headache, vision changes, swelling, or nausea, can point to a liver-related complication such as preeclampsia, and needs to be checked. Pain that spikes after fatty meals can sometimes be a gallbladder issue, which pregnancy also makes more likely. And any rib or chest pain that comes with shortness of breath deserves a call too, just to rule out anything cardiovascular or respiratory.

None of this means you should panic over ordinary end-of-day soreness. It means: mention it to your clinician at your next check-in regardless, and don't wait if it arrives suddenly or with those other symptoms attached.

Lateral Rib Breathing: The Pilates Tool That Helps Most

Classical Pilates teaches breathing into the sides and back of the rib cage rather than just the belly or the chest — we call it lateral or thoracic breathing. It's useful for everyone, but it does something specific for a pregnant body: it asks the ribs to expand sideways and backward, into space that isn't being crowded by the uterus, instead of trying to expand forward and down into territory the baby already occupies.

Try it seated or side-lying, which is both more comfortable and safer than lying flat on your back once you're past roughly 20 weeks. Wrap your hands or a scarf around your lower ribs. Inhale and feel the ribs push out sideways against your hands; exhale and feel them narrow back down, without collapsing your posture. A few slow rounds, a few times a day, genuinely changes how much room your lower ribs feel like they have. It won't move the baby, but it retrains the breath to use the space that's actually available, which takes real pressure off the joints that are complaining.

Side-Lying Openers and Daily Posture Habits

Because rib pain tends to concentrate on one side, side-specific stretching tends to help more than generic ones. A gentle seated or side-lying reach — extending the arm on your sore side up and over, lengthening that side of the rib cage while you breathe laterally into it — is a modified version of the Mermaid stretch adapted for pregnancy, kept small and controlled rather than a deep lateral flexion. Hands-and-knees "thread the needle," reaching one arm underneath your body and rotating gently, is another good option once lying prone or fully twisting is off the table.

I tell clients to think of it as making space, not fixing a problem. You're not undoing the pain, you're giving your ribs somewhere better to go.

Aviva Reinhart

Outside of exercise time, posture does a surprising amount of the work. A "swayback" stance — ribs pushed forward, pelvis tucked under — is common late in pregnancy and adds load to the front of the rib cage; stacking your ribs back over your hips, rather than letting your belly lead, takes some of that pressure off. Standing and seated breaks every 30 to 60 minutes if you're at a desk, a pregnancy support band if you're on your feet a lot, and side-sleeping with a pillow between your knees and another supporting your belly all help, mostly by keeping you out of the positions that compress the ribs for long stretches.

What to Avoid as Your Ribs Get Sensitive

A few things tend to make rib pain worse rather than better. Lying flat on your back for exercise or stretching after about 20 weeks is the biggest one — it's uncomfortable for sensitive ribs and, separately, it's not recommended in later pregnancy because it can compress the vein that returns blood to your heart. Deep twists and full spinal flexion (think a classic, unmodified Pilates Roll-Up or Saw) ask the rib cage to do more than it wants to right now, and anything that compresses the front of your abdomen — including some ab-focused reformer work — can aggravate rib pain alongside its other pregnancy considerations. This is a good stretch of pregnancy to trade intensity for precision: smaller ranges, more side-lying and seated and standing work, and an instructor who knows you're pregnant and can offer the modification in the moment rather than guessing.

Where to Start

If your ribs have started complaining, start with the breath before you start with exercises: a few minutes of lateral rib breathing, seated or side-lying, once or twice a day. Add one side-specific opener — the modified Mermaid reach or thread-the-needle — on whichever side feels tighter, and pay attention to how you're standing and sitting the rest of the day, since that's often doing more damage than any single workout. If you're already in a prenatal Pilates class, tell your instructor specifically where it hurts; a good one will adjust the session on the spot rather than running you through a generic routine. And keep that one conversation with your midwife or OB on the calendar, not because rib pain is usually serious, but because it's cheap reassurance either way. Most people find this particular discomfort fades once the baby's position shifts in the final weeks, or resolves on its own shortly after birth — which doesn't make it fun to live with now, but does mean you're not stuck with it.

Frequently asked

Is rib pain during pregnancy normal?

Yes, it's very common, especially in the second and third trimester. It's usually caused by the hormone relaxin loosening the rib joints combined with the growing uterus pushing up from below. It typically eases once the baby's position shifts or after birth.

Why does pregnancy rib pain usually happen on one side?

Many people already carry mild asymmetry through the rib cage, often more tension on the right side near the liver and diaphragm. Pregnancy posture changes tend to exaggerate that existing pattern, so one side often aches more than the other.

Can I keep doing Pilates if my ribs hurt?

Yes, most people can, with modifications. Favor seated, side-lying, and standing positions over lying flat on your back, skip deep twists and full spinal flexion, and lean on lateral rib breathing and side-specific stretches instead.

When should rib pain in pregnancy prompt a call to my doctor?

Call the same day if right-sided rib pain comes with a headache, vision changes, swelling, or nausea, since this can signal a liver-related complication. Pain that spikes after fatty meals or comes with shortness of breath also deserves a call.