Core during Pregnancy

Understanding your core as a system

image by Brit on Nappy

Given the amazing physical changes during pregnancy, it’s natural to wonder about core function and core exercise. Let’s clarify the core

image of diaphragm, abdominals, spinal muscles and pelvic floor comprising the core

Core = diaphragm + abdominals + spinal muscles + pelvic floor

Core Overview

Your core consists of 35 muscles working hard to keep you upright and stable in a variety of positions (whether you’re carrying laundry or opening the door). 

While the core is often considered as the belly abdominals, it actually consists of all of the muscles and tissues that attach to your spine and pelvis, including the diaphragm at the top and the pelvic floor at the bottom. 

Some core muscles even run the entire length of the spine, like the erector spinae.

Abdominal Muscle Layers

The abdominals are indeed a significant part of the core strength. They consist of several layers: the most superficial layer is the rectus abdominis (the so-called “six-pack”); next deeper, the obliques; and the deepest layer, the wrap-around transverse abdominis (TVA or “corset muscle”). 

Connective tissue weaves all of these muscles together into a network. For instance, the linea alba connects the rectus abdominis in the front. 

The multifidus, quadratus lumborum and erector spinae are some of the muscles that make up the core muscles at the back of the body. Note that the internal obliques, often thought to be a “front” abdominal muscle, wrap all the way around to the back to connect to the spine.

Your pelvic floor is an incredible sling of multiple muscles supporting your organs and belly. These muscles constrict and lift to provide core stability and support abdominal organs but also release and lengthen for bowel/bladder function and for birth. For more detail on the pelvic floor, check out this beginner’s guide from Pelvic Guru

Superior view of the pelvis and pelvic floor muscles.

(looking down from the top of the body)

Interior view of the pelvis and pelvic floor muscles including the outlets for the urethra, vagina, and rectum (top to bottom).

(looking up from the bottom of the body)

Core as a System

Your core is a system that uses breath and the aforementioned muscles to create and release pressure. You can feel it in action with this experiment: 

What did you observe? When you inhaled, you may have noticed your chest and your belly expanded. When you exhaled, your belly and chest drew in, either together or in sequence.

As you inhale, your diaphragm moves down, takes up space in your abdominal cavity, which increases pressure and causes your belly to create space, too. Your pelvic floor creates space as well by softening. (This can be harder to notice.) When you exhale, your diaphragm and belly return as the breath leaves and no longer takes up space. Your pelvic floor lifts at the same time. This is the natural rhythm of breath within your core. 

Let’s practice beginning to feel those deep muscles. Do the same three-breath exercise from above with your hands on your belly, now with more intention. 

Do this inhale-relax-and-exhale-lift a few more times. You just did a subtle, yet fantastic, core workout. 

Pregnant Belly and Organs

Pregnancy and Core

So how does adding a baby, placenta, and amniotic fluid all fit into this system during pregnancy? Doesn’t something have to give?! 

Luckily, those same core tissues and muscles—including your pelvic floor and abdominal wall—stretch and make space in your amazing changing body with the help of pregnancy hormones including relaxin. 

As your baby and placenta grow, your uterus increases in size (up to 5x) and ascends out of the pelvis into the abdominal cavity. 

The muscles and tissues of your abdominal wall lengthen and the linea alba stretches. This stretch, distancing, or separation is a way for your body to adapt and make space for that baby! Most pregnant people will have some distancing, or diastasis, but the amount depends on factors from activity to size or number of babies. Also, your rib cage expands laterally with the circumference increasing by 10-15 cm. So, if you’re wearing a bra, this might explain why you need a larger bra or extender! Check out this amazing visualization from the Museum of Science and Industry in Chicago. It clearly shows the pregnant belly and organs changing week to week. 


Our fresh understanding of the core system, its pressures and connection to the breath, can answer some of the common questions about pregnancy and exercise: 


Remember, even simply at rest, your core muscles and tissues are already supporting the weight of your pregnancy without undertaking any type of exercise or movement. While exercising and moving your pregnant body, it is beneficial to connect your breath with your core movement. Exert on the exhale!

Understanding how your body works empowers you to make choices throughout your day to better protect your pregnant body.  Begin to connect more with your breath, abdominals and pelvic floor to understand what is best for you. 

Article by Carry cofounder Heather Christine, prenatal & postpartum yoga teacher, birth doula, doula trainer, physical therapist, and parent of three living in Minneapolis, MN. 

Pelvis and Pelvic Floor images photographed by BRAVA Core & Pelvic Floor for Birthworkers.

Pelvic Guru images: permission for use granted to the author of this article as a member of the Global Pelvic Health Alliance (GPHAM). For information on access to illustrations, courses, and the largest global pelvic health directory, visit

Black Fetus Illustration: © Chidiebere Ibe. Adapted from the original illustration © QA International, 2010. 

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