A peanut ball is a large inflatable ball shaped like a peanut shell, with a narrow indentation in the middle and rounded ends. It’s most commonly used during labor and delivery to help open the pelvis and shorten labor, especially for people with epidurals who can’t easily move around. Peanut balls also have a second life in pediatric physical therapy, where they help children build core strength and balance.
Shape, Size, and Design
Unlike a standard round exercise ball, a peanut ball has a curved, hourglass-like shape. That midline indentation is what makes it useful: it can be placed between or under the legs without rolling away, which a round ball can’t do. The balls are made of thick, durable plastic and come in four sizes based on the user’s height.
- 40 cm: For people under 5’3″
- 50 cm: The most common size, for people 5’3″ to 5’6″
- 60 cm: For people 5’7″ or taller
- 70 cm: Used only for sitting on or straddling
The right size also depends on hip-to-ankle length and what position you’re using it in. A semi-sitting position may call for a smaller ball, while other positions may need a larger one for the same person.
How It’s Used During Labor
The peanut ball was developed largely to solve a specific problem: people who get an epidural lose much of their ability to move, stand, or squat during labor. Those upright, active positions help the baby descend through the pelvis, so losing them can slow things down. The peanut ball lets someone lying in bed mimic the pelvic opening that happens during a squat.
The most common position is side-lying with the peanut ball placed between the knees or thighs. This keeps the legs apart and the pelvis wide open, encouraging the baby to rotate and move downward. Nurses or midwives can adjust the ball’s placement to change the angle, and they’ll typically switch sides every 30 to 60 minutes. The ball can also be used in a semi-sitting position in bed, tucked under one leg to create asymmetry in the pelvis, which can help a baby who’s in an awkward position find a better path down.
Because the peanut shape stays put between the legs, it’s stable enough for someone who has limited sensation or mobility from an epidural. A round birthing ball, by contrast, works best when someone can sit upright on it, rock their hips, or lean over it on their hands and knees. Both tools aim to keep the pelvis mobile, but they serve different situations.
What the Research Shows
A randomized trial published in a major obstetrics journal found that using a peanut ball with specific positioning reduced the active phase of labor by an average of 82 minutes and total labor duration by about 89 minutes compared to standard care. Women in the peanut ball group also reported higher satisfaction with their birth experience, scoring about 1 point higher on a 10-point scale.
The evidence on cesarean delivery rates is also encouraging. A meta-analysis pooling data from seven studies and over 1,000 women found that peanut ball use was associated with a 26% lower risk of cesarean delivery. Among women who had epidurals specifically, the reduction was 23%. In practical terms, that translates to roughly 69 fewer cesarean deliveries per 1,000 births. The exact mechanism isn’t fully understood, but the working theory is that the ball opens the pelvic outlet and improves the effectiveness of contractions by keeping the body in a more favorable position.
Peanut Ball vs. Round Birthing Ball
Round birthing balls (the same as a Swiss ball or gym ball) have been used in labor for years. People sit on them, rock their hips in circles, or lean forward over them on hands and knees. They’re excellent for staying active and mobile during early labor before an epidural, relieving pressure on the tailbone and lower back.
The peanut ball fills a different role. Its shape makes it usable while lying down, which is why it became popular specifically for people with epidurals. A round ball allows more hip rotation, but it requires balance and leg strength that an epidural takes away. The peanut ball sacrifices some of that rotational freedom in exchange for stability in bed. Many hospitals keep both on hand and use them at different stages of labor depending on what the person needs.
Uses Beyond the Delivery Room
Peanut balls are also a staple in pediatric physical therapy, where their shape offers a stable but dynamic surface for children working on strength and coordination. The NAPA Center, a pediatric therapy organization, recommends several exercises that take advantage of the ball’s unique shape.
For core strength, a child can straddle the ball with feet on the floor. The slight instability challenges their trunk muscles and postural control without the risk of rolling off a round ball. Lying stomach-down over the ball and walking the hands forward on the floor builds upper body strength and motor planning. Kids working on balance can stand with one foot on the floor and the other on the ball, which builds hip and ankle stability as a stepping stone toward standing on one foot independently.
The ball also has sensory benefits. For children who seek deep pressure input, rolling a peanut ball over their body while they lie on a mat provides the kind of firm, even pressure that can help them feel calm when they’re overwhelmed. Therapists use this as a regulation tool for kids with sensory processing differences.
For children who can’t yet hold a hands-and-knees position on their own, the peanut ball placed under the belly provides support while still letting them bear weight through their arms and legs. This makes it a practical bridge between assisted and independent movement for kids building foundational motor skills.