A birthing ball is a large, inflatable exercise device designed for use during pregnancy, labor, and postpartum recovery. It offers a soft, supportive surface that encourages movement and upright positioning. Selecting the correct diameter is the most important consideration for safety and effectiveness. A ball that is too small or too large prevents the user from achieving the necessary ergonomic posture, making precise size selection essential.
Determining Your Birthing Ball Size
The initial selection of a birthing ball size is directly correlated with the user’s height to ensure proper alignment when seated. Manufacturers typically produce balls in three main diameters: 55 centimeters, 65 centimeters, and 75 centimeters. These standard measurements serve as a reliable starting point for finding the appropriate fit.
For individuals under 5 feet, 4 inches (162 centimeters), a 55-centimeter ball is generally recommended. This smaller diameter allows shorter users to keep their feet flat on the floor while maintaining the proper relationship between their hips and knees. The most common size is the 65-centimeter ball, which is suitable for people ranging from 5 feet, 4 inches up to 5 feet, 10 inches (162 to 177 centimeters).
Taller users, measuring 5 feet, 10 inches (177 centimeters) and above, should select the largest standard size, the 75-centimeter ball. If a person’s height falls exactly between two recommended sizes, choosing the next size up is often advisable. This provides a slightly higher sitting surface, which is preferable for promoting optimal pelvic positioning during labor, but this initial selection must always be confirmed by a posture check.
The Posture Check
Once a ball is sized according to height, the next step is a physical posture check to verify the fit for your unique body structure. When sitting on the ball with both feet flat on the floor, the hips must be positioned slightly above the knees. The angle created at the knee joint should be slightly greater than a right angle, ideally between 90 and 100 degrees.
This slight elevation of the hips (about 5 to 10 centimeters higher than the knees) is necessary for several biomechanical reasons. Maintaining this specific position helps to open the pelvic inlet, encouraging the baby to descend and engage for birth. The elevated posture also helps to relieve pressure on the lower back and tailbone, reducing back pain associated with late-stage pregnancy. If the knees are higher than the hips, the ball is too small or under-inflated, which can narrow the pelvic opening, defeating the purpose of using the ball.
Inflation and Maintenance
The degree of inflation significantly impacts the ball’s effective size and seated posture. A new birthing ball should not be inflated to its maximum diameter immediately, as the material needs time to stretch. Inflate the ball to about 80% of its intended size, allow it to rest for several hours, and then complete the inflation to the final size.
The ball should feel firm when pressed, but still have a slight give for comfortable bouncing and movement. Under-inflation causes the hips to drop too low, recreating the posture issue of a ball that is too small. Conversely, over-inflating the ball beyond its recommended diameter can compromise the material’s safety and increase the risk of a burst.
It is important to select a ball made with anti-burst technology, which is designed to deflate slowly if punctured. Always use the ball on a non-slip surface and check the firmness regularly, as air pressure may decrease over time. Keeping the ball consistently inflated to the proper firmness ensures that the correct hip-to-knee angle is maintained throughout your pregnancy and labor.