One of the most helpful tools during pregnancy is a pregnancy ball (also called a birthing or exercise ball). It can support your lower back, encourage better posture, help with baby positioning, and even prep your body for labor, no matter what trimester you’re in.
It’s also one of those things you don’t realize you need… until you sit on one and suddenly your back says thank you.
That said, choosing the right size really matters. A ball that’s too small or too big can actually cause discomfort in your hips, knees, or lower back. The right size, on the other hand, helps your body move naturally and comfortably.
If you’re looking for an easy, all-in-one option, the Momcozy BirthEase Maternity Exercise Ball Set is a popular choice that includes everything you need to get started. You can check it out here:
👉 Learn more about the Maternity Exercise Ball Set
Choosing a Pregnancy Ball Based on Your Height
The easiest way to find the right size is by your height. When you sit on the ball, your feet should be flat on the ground and your knees should be level with or slightly lower than your hips.
Use this quick guide:
- Under 5’0″: 45 cm ball
- 5’0″–5’4″: 55 cm ball
- 5’5″–5’11”: 65 cm ball
- 6’0″–6’3″: 75 cm ball
- Over 6’3″: 85 cm ball
If you’re between sizes, think about how you’ll use it. A slightly smaller ball tends to feel more stable, while a larger one allows for more stretch and movement.
How to Pick the Right Size
Beyond height, here are a few things to keep in mind:
Start with posture
You should be able to sit upright comfortably, without leaning forward or straining your back.
Think about how you’ll use it
- Sitting or working: you’ll want a stable ball where your hips are slightly higher than your knees
- Stretching or exercise: a larger ball gives you more range of motion
- Labor prep: comfort and stability matter most, especially if you plan to bounce or move on it
Check the inflation
A properly inflated ball should feel firm but still have a little give. If it’s too firm, it may feel unstable. Too soft, and it won’t give you enough support.
And yes, you’ll probably question if you inflated it correctly at least once.
Using a Pregnancy Ball by Trimester
Your height determines your size, but how it feels can change throughout pregnancy.
First Trimester
You’ll likely use it for light stretching, posture support, and gentle core engagement. Your standard size should feel comfortable here.
Second Trimester
As your belly grows, many people use the ball more for hip circles, pelvic movement, and relieving back tension. Most people stick with the same size.
This is also when sitting on it starts to feel way better than most chairs.
Third Trimester + Labor Prep
This is when a pregnancy ball really shines. It can help:
- Open the pelvis
- Improve posture during labor
- Relieve lower back pressure
Some people prefer a slightly larger ball at this stage for more hip opening, but it’s not necessary if your current one still feels stable.
Why the Right Size Matters
Using the correct size can make a noticeable difference in how your body feels day to day.
Better posture
It naturally encourages you to sit upright and engage your core without slouching.
Less back and hip pain
Gentle bouncing and movement can ease tension in the lower back and hips.
Improved pelvic mobility
A properly sized ball allows your pelvis to move freely, which can help with baby positioning and labor prep.
Better circulation
When your hips and knees are aligned, it supports healthy blood flow and can reduce swelling.
A comfortable alternative to a chair
Many people use a pregnancy ball at home or even at a desk, especially later in pregnancy, because honestly… regular chairs just don’t hit the same anymore.
Signs Your Ball Isn’t the Right Size
Your body will usually tell you if something feels off. Watch for these signs:
- Knees are higher than your hips – the ball is likely too small
- Hips are much higher than your knees – the ball may be too big
- You feel unstable or off balance
- You notice pain or numbness after sitting
The Bottom Line
So, what size pregnancy ball do you need? For most people, it comes down to your height and how you plan to use it.
The goal is simple:
- Knees level with or slightly below your hips
- A stable, comfortable seat
- Enough support for movement, stretching, and rest
Choosing the right size (and a quality option like the Momcozy BirthEase Maternity Exercise Ball Set) can make a big difference in how you feel day to day and help you stay more comfortable as your body prepares for birth
Brittany is a proud mom to two fun loving kiddos, Grayson and Audrey. With a passion for health and fitness, she’s a certified personal trainer and nutritionist who enjoys helping others lead active, enjoyable lives. When she’s not coaching clients, you can find Brittany, her husband, and her kids exploring Michigan’s vibrant scene of indoor play centers, parks, eateries, and events. Whether they’re discovering new hiking trails, celebrating local restaurant openings, or spending the afternoon at the cider mill, they’re always on the lookout for their next adventure. Brittany is passionate about sharing her family’s experiences to help other parents create lasting memories in Metro Detroit. You can follow along with her and her crew here @brittmilesxo.