It sometimes feels like the whole internet is talking about core muscles. But what are the core muscles anyways? And how does the core support my pregnancy and change after delivery?

Many people think of the “core” as the abdominals….the six-pack muscles, or the obliques. Not true.

The “core” is a series of 4 muscles; the transversus abdominis, the multifidus, the diaphragm and the pelvic floor.

The Core Cylinder System

These 4 muscles work together, in a coordinated system to help stabilize the body, support the organs (and baby), to protect the spine, the keep you from leaking urine, gas and feces, and to help with your breathing. And that is just the beginning of the wonderful things that the core muscle system does for you!

Core Cylinder Muscle System

The 4 muscles of the core cylinder system.

The Diaphragm

The top of the core is the diaphragm. This is our breathing muscle. The diaphragm pulls the lungs down and out allowing them to fill with air. It has a strong relationship with the pelvic floor (more on that later) and is often the first muscle in the core system that we begin to train after birth. After all, a baby has been shoved up into it for a number of months!

The Pelvic Floor Muscles

The pelvic floor is the bottom of the core. These muscles start at the pubic bone in the front and sling between the legs to attach to the tailbone in the back. They help to support the pelvic organs, maintain urinary/fecal continence, have a role is sexual function, and are the muscles that can be damaged from tears during vaginal birth.

The Transversus Abdominis

The transversus abdominis (or TA for short) is a deep abdominal muscle that acts much like a girdle, wrapping around the abdomen. It helps to pull the thorax together. While it’s the rectus abdominis (six-pack) that gets all the attention in pregnancy when it comes to abdominal separation, it’s the TA that helps to reactivate and rehabilitate an abdominal separation. Want to learn more about abdominal separation? See our post all about diastasis recti here.

The Multifidus

The multifidus muscles are a series of smaller muscles that run along the spine and help to stabilize the vertebrae.  They also help to support he spine and the rest of the core muscles. They can be strong or weak, coordinated or not.

How is my core affected by pregnancy and birth?

All of the core muscles have to cope with more strain during pregnancy, due to a growing uterus and baby. And depending on the type of delivery (vaginal or cesarean) we see different injury to the core muscles. Perineal tears can injure the pelvic floor muscles. Cesarean delivery can affect TA activation. A baby growing into the diaphragm can lead to difficulty breathing. Low back strain can make for multifidus changes. Not everyone has injury or muscle problems during and after pregnancy, but we do recommend preparing the core to the best of your abilities! Or, alternatively, rehabilitating after childbirth.

We hope that this helped to explain the core muscles! As always, if you have questions please feel free to reach out.


Looking to prepare your core and pelvic floor for birth? Check out our online course here.

Katie & Eryn

Motherhood Link