Most pregnant people need a 65cm exercise ball. That’s the right size if you’re 5’8″ or shorter. If you’re taller than 5’8″, go with a 75cm ball. The goal is to sit with your feet flat on the floor and your hips slightly higher than your knees, about 4 inches higher to be precise.
Size by Height
The sizing is straightforward:
- Under 5’4″: A 65cm ball inflated only to about 60cm (24 inches) in height. Slightly under-inflating a standard ball gives you the right seat height without needing to buy a smaller size.
- 5’4″ to 5’8″: A 65cm ball, fully inflated.
- Over 5’8″: A 75cm ball.
These are starting points. The real test is how the ball feels when you sit on it. Your knees should bend at roughly a 90-degree angle with both feet flat on the ground. If your knees ride up toward your chest, the ball is too small. If your feet dangle or you feel like you’re perched up high, it’s too large. A ball that’s slightly too big can always be under-inflated to bring the seat height down, which makes the 65cm a versatile choice for most people.
What to Look for When Buying
A standard gym ball and a ball marketed as a “birth ball” are essentially the same product, but quality varies widely. The single most important feature is anti-burst construction. A ball with this rating won’t pop suddenly if punctured. Instead, it deflates slowly, giving you time to get off safely. This matters a lot when your center of gravity is shifted forward and a sudden fall could be dangerous.
Beyond anti-burst construction, look for a weight capacity of at least 300 pounds. This accounts for your body weight, the weight of pregnancy, and the downward force of bouncing or rocking. Balls rated under 250 pounds are a red flag. Thicker material (2mm at minimum, 3mm ideally) holds up better over months of daily use. A non-slip surface texture helps the ball grip the floor and keeps you from sliding, especially on hardwood or tile. Choose phthalate-free materials, since phthalates are chemical softeners you don’t need exposure to during pregnancy.
How to Inflate It Correctly
Most exercise balls come with a hand pump. Inflate the ball until it feels firm but still has some give when you press into it with your hand. You should be able to make a small indent, roughly an inch or so, when you push down. A rock-hard ball is less stable and less comfortable. A very soft, squishy ball won’t support your pelvis properly.
If you’re on the shorter side, remember that you can deliberately under-inflate to lower the seat height. Measure the ball’s height from the floor to the top after inflating. You can always add or release air over the first few days as you figure out what feels right. The ball will also stretch slightly with use over the first week, so you may need to top it off once.
Why the Ball Helps During Pregnancy
Sitting on an exercise ball keeps your pelvis in an open, slightly forward-tilting position. This takes pressure off your lower back in a way that a couch or office chair simply can’t match, because those surfaces tend to tuck your pelvis under and round your spine. On a ball, your body naturally finds an upright alignment.
Gentle rocking and tilting while seated, moving your hips side to side, front to back, or in circles, keeps your hip joints and lower back mobile. This is especially useful in the third trimester when everything stiffens up and pelvic girdle pain becomes common. Many people find that replacing their desk chair or couch time with 20 to 30 minutes on the ball noticeably reduces low back soreness.
The ball also helps with fetal positioning. The open pelvis and gentle movement can encourage the baby to settle into a head-down, anterior position, which is the ideal orientation for labor. Sitting upright with a forward pelvic tilt gives the baby more room to rotate compared to reclining on a sofa.
Using the Ball to Prepare for Labor
In the weeks before your due date, regular time on the ball can help your body get ready for delivery. The gentle pressure of the baby’s head against your cervix while you sit upright encourages natural softening and ripening of the cervix. Rocking and bouncing help the baby descend deeper into the pelvis.
During labor itself, many people use the ball in several positions. Sitting and gently swaying helps manage contractions in early labor. Kneeling on the floor and draping your upper body over the ball takes weight off your back during intense contractions. You can also use the ball while standing, leaning forward onto it against a bed or wall. These positions use gravity to assist the baby’s descent and give you something active to do with your body during contractions, which helps with pain management and reduces tension.
Research on birth ball use during labor has found that the movement and positioning can help guide the baby through the pelvis when the baby is in a less-than-ideal position, such as facing sideways or toward your front instead of toward your back. The ability to rock freely on the ball for even 30 minutes during active labor gives you a tool for encouraging rotation.
Staying Safe on the Ball
Place the ball on carpet or a yoga mat rather than directly on hardwood, tile, or laminate flooring. Smooth surfaces let the ball slide out from under you, especially if you’re wearing socks. Bare feet or grippy shoes on a non-slip surface is the safest combination. Keep the area around you clear of furniture corners and hard edges in case you do lose your balance.
When getting on and off the ball, stand in front of it with your feet wider than hip-width apart. Reach one hand back to steady the ball, then lower yourself down. Don’t try to hop on from the side. When sitting, keep both feet planted firmly on the floor at all times. Having a wall, chair, or partner nearby to grab onto is helpful, especially as your belly gets larger and your balance shifts in the final weeks.